3 definitions
Definition.com
An Opposite (n.) lies very close to its word in our linguistic consciousness, so the wrong one is easily evoked.
Definition.com
A Slip of the tongue (n.) can come from two answers in the mind at once, intermixed — “it will last another month” and “it's a sad story” fuse into a word that never existed.
Definition.com
A Slip of the tongue (n.) let the President's secret wish break through as the opposite of what he meant: “Gentlemen, a quorum is present and I herewith declare the sitting closed!”