1. 放弃，拒绝接受（想法、计划等）
If you jettison something, for example an idea or a plan, you deliberately reject it or decide not to use it.

2. 丢弃；处理掉；摆脱
To jettison something that is not needed or wanted means to throw it away or get rid of it.

1. throw as from an airplane

2. throw away, of something encumbering