B1
to make a happy or friendly expression in which the corners of your mouth curve up
Dictionary examples:
He smiled to himself. (14.3)
He smiled and shook my hand. (21.3)
When he smiled at me I knew everything was all right. (26.9)
He smiled politely as Mary apologized for being late. (27.8)
I couldn't help smiling when I thought of how pleased she was going to be. (29.1)