Sheepish (adjective)

1. Timid, bashful, or shy, especially in a playful or endearing way.
2. Embarrassed or ashamed.

Origin:

Middle english sheepisch, from old english scēpisc "like a sheep".

Examples:

1. He had a sheepish grin on his face when he admitted he'd forgotten her birthday.
2. She felt sheepish when she realized she'd been singing loudly in public.
3. He looked sheepish when he was caught stealing cookies.
4. She gave a sheepish smile when she was asked if she had cheated on the test.
5. He was sheepish when he asked for directions.