Wordnet 3.0
NOUN (1)
1.
a word invented (usually unwittingly by subtracting an affix) on the assumption that a familiar word derives from it;
The Collaborative International Dictionary of English v.0.48:
back-formation \back"-for*ma`tion\ n. (Linguistics)
1. a word invented (usually unwittingly by subtracting an
affix) on the assumption that a familiar word derives from
it, such as emote from emotion.
[WordNet 1.5 +PJC]
2. the process of inventing a back-formation[1].
[PJC]
WordNet (r) 3.0 (2006):
back-formation
n 1: a word invented (usually unwittingly by subtracting an
affix) on the assumption that a familiar word derives from
it