Smug (adjective)

1. Having or showing a complacent sense of self-satisfaction.
2. Having an excessive pride in one's own abilities, appearance, etc.

Origin:

The word 'smug' originated from the middle english word 'smogen', which means 'to look self-satisfied or pleased with oneself.'.

Examples:

1. He looked smug when he told us he had gotten the promotion.
2. Her smug attitude made everyone in the room dislike her.
3. The smug look on his face was all the evidence I needed.
4. His smug grin was almost more than I could bear.
5. She gave a smug smile and walked away, satisfied with herself.