Used in negative constructions to indicate irritation, aggravation, or discontentment. Primarily heard in UK. I'd lie low for a while if I were you. The boss is not best pleased about what happened. A: "So, what do you think?" B: "Well, I can't say I'm best pleased about where they decided to build the shed. It's in such an inconvenient spot!" I don't imagine Mum would be too best pleased to find her car missing for the afternoon, do you?
See also: please
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.