From
http://www.answers.com/topic/weaselwea·sel (we'z?l)
n.
Any of various carnivorous mammals of the genus Mustela, having a long slender body, a long tail, short legs, and brownish fur that in many species turns white in winter.
A person regarded as sneaky or treacherous.
intr.v., -seled also -selled, -sel·ing -sel·ling, -sels -sels.
To be evasive; equivocate.
phrasal verb:
weasel out Informal.
To back out of a situation or commitment in a sneaky or cowardly manner.
[Middle English wesele, from Old English wesle.]