noun
cut end; section; opening; slit
Refers to the surface or edge created by cutting something, or an opening/slit made by a cut. 切り口 is a more common variant.
See also: 切り口
木の切れ口がささくれ立っている。
The cut end of the wood is splintered.
封筒の切れ口から手紙
Take the letter out through the slit in the envelope.