Chambers 20th Century Dictionary(0.00 / 0 votes)Rate this definition: 1  Post. pÅst, n. a piece of timber fixed in the ground, generally as a support to something else: a pillar.âv.t. to fix on or to a post, or to any conspicuous position, in a public place: to expose to public reproach, to placard as having failed in an examination, &c.ân. 2  Post.