a hole dug in the earth for setting in the end of a post, as for a fence.
Archaeology. an excavated hole showing by its shape and by the remains of wood or other debris that it was once filled by a post.

Origin of posthole

First recorded in 1695–1705; post1 + hole Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for post-hole

Historical Examples of post-hole

Word Origin and History for post-hole

1703, from post (n.1) + hole (n.).

Online Etymology Dictionary, © 2010 Douglas Harper