to get something, using effort, by chance or in a way that has not been explained

Cheap organic food is still difficult to come by. 便宜的有机食品仍然很难买到。

I'd like to know how she came by that black eye. 我想知道她眼眶又青又肿是怎么弄的。

to visit a place for a short time, often when you are going somewhere else

I'll come by (the office/your house) one day this week and we can have a chat. 这周哪一天我顺道去（办公室／你家），我们可以聊一聊。