Exchanging tiles or playing a low-scoring word in the hope of being able to play a bingo the next turn. See Bingo and High Probability Tiles.
(A.K.A. DUMPING) To play only one or two tiles, usually for few points, keeping five or six really good tiles, with the hope of playing a high-scoring word next turn.
Throwing out one tile in the hope of picking up a specific tile to make a bonus word: e.g. discarding the R from the rack Q-U-E-T-R-A-L in the hope of picking up the Z to make QUETZAL. DISHING is discarding one tile with the high probability of forming a bonus with the new letter: e.g. discarding the Q from the rack S-A-T-I-R-E-Q. WISHING is exchanging all seven tiles in the hope of picking up a seven-letter word.