堑

东非大地堑

dōng fēi dà dì qiàn

Great East African rift valley

吃一堑，长一智

chī yī qiàn , zhǎng yī zhì

Fall into the moat and you'll be wiser next time (idiom); One only learns from one's mistakes.

地堑

dì qiàn

trench, rift valley

堑壕

qiàn háo

trench; entrenchment

堑壕战

qiàn háo zhàn

trench warfare

天堑

tiān qiàn

natural moat

路堑

lù qiàn

(civil engineering) cutting (for a railway or highway)