Starcraft – the infamous “Archon Toilet”

A timing push involves making an attack at a certain point in your build order, such that the attack coincides with the completion of a researched upgrade, or a certain mass of units.

For example: you might see a Terran Bio timing push, where the Terran player moves his forces out such that Stimpack technology will have just finished as they reach the enemy forces.

Also applies to Weapon / Armor upgrades. Since the Weapon / Armor upgrades often completely cancel each other out, it's best to start fights when you have the upgrade, and your opponent does not. If you wait too long, your opponent (if they know what they're doing) will complete their own counter-research, and your advantage will be lost.

Hence, timing push; Timing an attack such that it occurs when you have the momentary advantage.

Try http://day9tv.blip.tv/posts?view=archive. This is his main archive; this is the best source of vids.

The one I think you are referring to is Day[9] Daily #252 - Secrets of Hotkeys, APM and Mouse Movement