means Feeling or showing an irritating excess of satisfaction with oneself or one's situation.

from Smug started life looking, well, polished — it comes from Low German 'smuk,' meaning neat, trim, or pretty, a cousin of the Dutch 'smuk' (finery, ornament). In the 1500s English borrowed it as a compliment: 'smug' meant sleek, spruce, well-groomed. But there's a thin line between looking pleased with how you've turned out and being pleased with yourself, and by the 1700s the word had slid down it entirely — neat on the outside, insufferable underneath.