Covert activities or situations are secret or hidden.
例句
They have been supplying covert military aid to the rebels...他们一直在暗地里向叛乱者提供军事支援。The depth of covert racism in my own profession frightens me.我所从事的职业中暗藏着如此深的种族主义偏见，这让我感到害怕。
N-COUNT
(小动物或猎禽可藏身的)矮树丛，灌木丛
A covert is a group of small trees or bushes very close to each other where small animals or game birds can hide.