What does TTK mean

There are several server options that affect weapon damage in Team Fortress 2, and they're often confused:

Weapon Spread -- With this turned on, hitscan weapons, such as shotguns, will have the same non-random pattern of "bullets" each time they are used. Default is ON.

Damage Spread -- Each weapon normally has a minimum and maximum damage. No Damage Spread means that each weapon will do a set, average, damage rather than varying between attacks. Default is ON. (Critical hits always do 3 times damage)

Damage Falloff -- Normally, the damage dealt by a weapon decreases the farther away you are for your target. If this is turned off, A rocket detonating right next to you and a rocket shot from the opposite side of the map will do equivalent damage. Crits are never affected by Damage Falloff. Default is ON.

The default is to have Damage Spread ON. Nodmgspread refers to servers which have turned it OFF.

Zoning: Intentionally keeping distance/pressure on your opponent, either reading their style or forcing them into playing a certain way. Adaptive to close combat situations and able to make good on big damage opportunities. (sic)
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A good zoning player will always create opportunities for themselves by keeping their opponent away from them as to gain control of the match, then adjust to their opponent's tactics/counters and act accordingly. (sic)
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Zoning doesn't have to involve repeated moves at all. Zoning isn't just keeping your distance, it's about keeping within a very specific distance, which may not even be a half screen away. It might be just barely within range of a normal move. The idea is to establish this distance and keep it, because it limits your opponent's options and allows you to react more easily, giving you the control of the match.

Source: http://www.trmk.org/forums/showthread.php/22827-The-Difference-Between-Zoning-and-Spamming