The term dirty trick has often been used to describe combinations of invalid tiles that lead to cooks (among other devices); its official use in Chip's Challenge mechanics is to describe an MS Ruleset-exclusive method of pushing blocks on sliding tiles when Slide Delay is in effect. It was named for its most official application in CCLP3 level 39, Cheap Shots and Dirty Tricks.
Requirements and mechanics
Sliding blocks are ahead of Chip in the move order and move at 10 m/s, which means that if Chip attempts to push a block onto a sliding tile that deflects straight back, normally there is no possible way to survive its return even by using a spring step, spring slide or boosting, as these all work at 10 m/s. The only remaining variable is slide delay, which instead of making Chip faster delays the block. A delay of  will keep Chip alive even at 5 m/s, while [1/2] will work at ten.
In the northwest section of Cheap Shots and Dirty Tricks, shown here, Chip enters either side of the area and collect another key and chips, but must push the block he reaches to one space from an opposing force floor. Without the dirty trick, this is impassable and Chip would have to enter from the other side, but earlier in the level blocks clone onto force floors and remain there for the duration of the attempt, provoking [1/2] of slide delay at any time. Assuming Chip enters from the north and pushes block 1 down, the dirty trick is executed exclusively by moving [1/2] DL, which puts Chip on the location of block 2 before block 1 moves. The section is then solved by opening the lower red lock and pushing block 1 U, such that there is room to move block 2 east.
There are no dirty tricks known in CC1, as the basic setup rarely appears.
The most obvious example in CCLP2 is Madness II. The bold time routes (with and without the Mouse Panel Glitch require a long stack of blocks built up on a sliding chain which lands in water; for Chip to remove the dirt safely, a spring step dirty trick is required, and is available because objects on the sliplist that don't move create slide delay. Another possible demonstration in CCLP2 (though it is not necessary for any reason) is Just Enough, where a teeth stays on the force floor at the start if it lands there and a block can be pushed onto a single, returning ice tile.
The dirty trick appeared slightly more often in CCLP3, but it was more explicitly defined as a specific technique and became more public as a result. Besides its namesake, it also appears in the bold route of Manic Depression in the spring slide form, where a block cloned from the start remains within [1/2] range of a second cloned block that keeps it from landing; the dirty trick gets Chip behind this block before it lands such that it can be pushed west into the teleport.
The technique also figures strongly into the possible solutions to the glider train section of You Can't Teach an Old Frog New Tricks; there are more solutions in MS than in Lynx, which is true for much of the level. Chip can catch block(s) sliding onto [6, 10/12] and push it to [6, 9] (though more often one from [6, 10], since the ice forces Chip to land on [6, 9] and use the dirty trick), and due to monsters trapped on force floors a boosting dirty trick is available.
Other occurrences appear to be possible, but are undiscovered or not public.