1. someone/something noticeably different from their surroundings
stick out like a sore thumb somewhere
If you 'stick out like a sore thumb' you are noticeable in comparison to the things or people around you. "Can you tell me if this outfit looks alright? I don't want to stick out like a sore thumb at the conference." "You can always tell when someone from creative comes to this office, they stick out like a sore thumb!" This is a casual expression but it could be insulting in the wrong context so be careful! Usually this expression as a negative connotation but it can be used to humorously jeer someone also.