Definify.com

Webster 1913 Edition

Verb.

[1st pref.

un-

say

To recant or recall, as what has been said; to refract; to take back again; to make as if not said.

You can say and

unsay

things at pleasure.

Goldsmith.

Verb.

pret. and pp. unsaid. To recant or recall what has been said; to retract; to deny something declared.

Say and unsay, feign, flatter or abjure.

unsay ‎(third-person singular simple present unsays, present participle unsaying, simple past and past participle unsaid)

To withdraw, retract (something said).
- 1851, Herman Melville, Moby-Dick:
  And in the first place, you will be so good as to unsay that story about selling his head, which if true I take to be good evidence that this harpooneer is stark mad [...].
To not have said (since this is physically impossible usually in the subjunctive, as I wish I could unsay).
There are somethings I'd like to unsay... to my boss... right before he decided to fire me.