Twee describes something that is trying so hard to be sweet and charming that it becomes annoying. Notice that the thing really is pretty — that is the whole point. A cottage with roses round the door, a café where the milk comes in tiny jugs and the menu is handwritten in curly letters, a song with whistling and glockenspiel in it, a shop selling cushions that say 'Home Sweet Home'. None of that is ugly. Calling it twee means you find the prettiness too much, too small, too safe — sweet in a way that has no strength or truth in it. So it is an insult, but a gentle one, and it says as much about the speaker's taste as about the thing; another person could look at exactly the same café and just call it lovely. It is strongly British — Americans use it much less and may say 'cutesy' or 'precious' instead. It goes before a noun or after 'be': 'a twee little village', 'the ending was too twee'. Comparative forms are tweer and tweest, but most people say 'more twee'. Oddly, in music the word turned round and became a name people are proud of: twee pop is a real style, and its fans call it that themselves.