Hello....
A dictionary says like below.
The two meanings seem to be contradictory to each other.
Is there any criteria to decide by?
Is it to be decided only by context?
One meaning is to participate, the other is not to participate....
sit out
v.1. To stay until the end of something:
Let's sit out this act, and then we can leave at intermission. This lecture is reallyboring—I don't think I can sit it out.2. To refrain from taking part in something:
The star pitcher sat out the game with an ankle injury. I'm going to sit thisdance out.http://idioms.thefreedictionary.com/sit+out