To stop by or drop in somewhere briefly (e.g., on the way home); to call at a place temporarily.
帰りに駅に立ち寄って切符を買った。
On the way back I stopped by the station and bought a ticket.
仕事帰りにコンビニに立ち寄った。
I dropped into a convenience store after work.
図書館に立ち寄って本を返してきた。
I stopped by the library to return a book.
友達の家にちょっと立ち寄って行くね。
I'll just drop by my friend's house for a bit.