Fetching details from the dictionary...

gap; opening; space
opportunity (to take advantage of); chance
discord; disagreement
カーテンの隙から光が差し込んでいる。
Light is coming through the gap in the curtains.
仕事の隙を見つけて休憩を取った。
I found a break in work and took a rest.
警備員の隙を突いて侵入した犯人だ。
The criminal who broke in by exploiting the guard's opening.