The Collaborative International Dictionary of English v.0.48:
Appeaser \Ap*peas"er\, n. One who appeases; a pacifier. [1913 Webster]WordNet (r) 3.0 (2006):
appeaser n 1: someone who tries to bring peace by acceding to demands; "An appeaser is one who feeds a crocodile--hoping it will eat him last"--Winston Churchill