Someone - I forget who it was - used this word recently in conversation. I've always known the general gist of what context the word can be used in and such, but I've never known the exact definition of it. So I looked it up in my trusty Canadian Oxford English Dictionary, and this is what I found:
Assuage (transitive verb)
1. Calm or soothe (a person, pain etc.).
2. Appease or relieve (an appetite or desire).
See also assuagement (noun), assuager (noun) [Old French as(s)ouagier, ultimately from Latin suavis sweet].