Give somebody/get a big hand
Definition 1 of 2
Pro Tip 1/3Audience Gesture
Used when people in the audience show their approval or support by clapping loudly together. 
After the curtain fell, the audience gave the actors a big hand.
Pro Tip 2/3Not Literal
The phrase is not about the size of a hand; it's a metaphor for clapping. 
The comedian finished his set and the crowd gave him a big hand.
Pro Tip 3/3Positive Achievement
Often used to congratulate someone after a performance or notable achievement. 
She won the chess tournament, so let's give her a big hand!