Sakigiri
Sakigiri 「先切り」 is the act of discarding potentially dangerous tiles early. This strategy sacrifices tile efficiency for the sake of defense, may the hand be looking to push tenpai or not at all.
Usage
Each turn, players draw and discard tiles. When playing for tile efficiency, it's best to keep useful tiles before useless ones. However, those tiles may become dangerous as the hand progresses. The idea behind sakigiri is to discard dangerous-but-useful tiles before opponents reach tenpai, to avoid dealing in.
Examples
Draw: 
The 7-pin and West are equally useless here. While number tiles are normally stronger than winds, the hand doesn't benefit from having the 7-pin. The hand is already at iishanten, so when it reaches tenpai, it will be discarded. Further, the hand already has good joints; the joints do not need to be upgraded. Therefore, both 7-pin and West are equal. Discard 7-pin first, because it could be dangerous later in the round.