Yes, of course! Whenever the fictions establishes it!
That means, whenever a PC (or NPC for that matter) is convincingly able to hit multiple targets, it can do so.
How do you handle that mechanically? You have the PC roll any defy danger and/or hack&slash as usual, let them roll their damage and apply the damage to every target hit.
On/around page 56 in the rule book (explanations below the Hack&Slash move) it is stated: "If the action that triggers the move could reasonably hurt multiple targets roll once and apply damage to each target (they each get their armor)."
Now what are the implications and consequences? Dungeon World is all about going with the fiction. High risk or difficulty of a task is not reflected by the roll (hence you will never find a difficulty adjusted roll in Dungeon World), but by the consequences on a miss. A miss on such an attack provides the GM with a truly golden opportunity for a hard move. As the PC put a lot of risk on the table, you can then choose to answer with an appropriately scaled harder hard move.
An example from an actual game of mine:
The group had just opened a big stone gate by solving a dwarven riddle. Behind it, some goblins were also trying to open the door (to escape the cave that was the lair of an undead chimera). When the groups' s Barbarian saw the cluster of goblins, he said: "I take my 2-hand sword and spin around, whirling through the crowd!" I had him roll defy danger on STR, because he was powering through a horde of goblins. He rolled a 7-9 and as a result had the choice to lose control over his Barbarian rage or get overwhelmed by the goblins.
He chose to let his fury go wild and sprawled through the goblins, dealing his damage to all of then and killing a lot of them (a horde of goblins minus a lot of goblins is still a horde though...). In the process, he lost grip of his sword and flung it down a slope.
And one thing should be clear to everybody after the first miss on a Barbarian's mighy cleave: being in the middle of a goblin horde with your sword flung to the other side of the cave is a glorious opportunity to satisfy some Barbarian appetites!
This is a difficulty that comes up in a lot of RPGs actually, including way back in the early editions of D&D (from which Rogue Trader gets its Disengage-to-avoid-bonus-attack rule).
Think of the round as being full of position and weapon maneuvers and potential attacks, but the roll is only made for the pivotal attack opportunity for which all the the feints and parries and ducks and weaves were softening up the enemy. In this way, the roll is an abstraction of all your careful efforts during the round. See the "Combat Abstractions" sidebar on page 234, where the rules instruct the reader to think of a combat round this way:
[Combatants] are constantly side-stepping, twisting, and ducking, to avoid attacks or assume more favourable combat positions.
And then, when your opponent suddenly flees without carefully disengaging, you can just straight up stab at them because they just gave you a golden opportunity for no effort on your part.
As for the strolling NPC, that's legal in Rogue Trader, apparently as a design choice. The only way you get your "opportunity attack" against a moving target that hasn't used Disengage is if they were already engaged in melee with you, and becoming engaged due to moving only happens when the movement ends adjacent to an opponent (Move p. 241; Engaged in Melee p. 247). Since they're not stopping, they're not engaged, and you don't get the free attack. (Contrast this with another system that uses the "Disengage" design for "opportunity attacks": in early D&D, you become engaged immediately upon becoming adjacent, making opponents "sticky" and enabling them to control their adjacent squares by forcing a Disengage to move again.)
Why that's legal is an aesthetic design choice, as far as I can see. You can rationalise it with a story, or you can object to it on tactical design grounds — but regardless it's RAW. The easiest rationalisation is that opponents who aren't anticipating the need to physically stop someone are unable to do so — they're busy with whatever else they decided to do that round and the opponent ducks and weaves through the battlefield to wherever they're going.
The tactical objection is that this makes it hard to control the battlefield! That's reasonable, but the intuition is likely conditioned by Pathfinder's (unrealistic but functional) way of managing battlefield control.
To accomplish movement control in Rogue Trader, instead of it happening passively as in Pathfinder, you have to use a mix of passive and active tactics. Passively, you can either completely block passage by standing shoulder-to-shoulder, providing no space for an opponent to move through; or you can spread your forces out such that their movement has to end adjacent to one of you. Of course, that passive kind requires a lot of bodies and coordination. Active prevention can be done more solo but with more effort investment, by anticipating the need to stop an advance — which is what the story above implies is the solution — and using the Delay action to attack the incoming opponent. Because attacking someone immediately makes them engaged in melee, they won't be able to continue their movement after your delayed attack, and will furthermore be forced to use Disengage later to continue toward their position objective.
Best Answer
You possibly could, but you'd almost certainly be better off with a different system.
Pathfinder is designed very heavily around the assumption that rolling initiative and taking turns is how combat progresses and is constrained. Dungeon World is designed around the assumption that combat is driven forward and constrained by player decisions. If you were to change Pathfinder to use Dungeon World's system of initiative, you would need to re-design, re-write and re-balance a huge number of character abilities, spells and effects (including, but not limited to, everything with a duration). To the best of my knowledge, no-one has ever tried to do this. You could conceivably do it yourself, but by the time you were done the game you'd have would only superficially resemble the Pathfinder it was based on; The rules content and game experience would be immensely changed.
Given the scale of work involved, it might be a lot easier to modify Dungeon World (or some other game that features apocalypse-style initiative) to include more of the language and flavour of Pathfinder, or just to use a different system that has apocalypse-style initiative built in.