Definition from Wiktionary, the free dictionary
Alternative forms 
- (colloquial) A take, commonly used as a comical reaction to a surprising sight, in which someone casually sees something, briefly stops looking at it, realizes what it is, and snaps attention back to it with an expression of surprise or disbelief.
- Smith passes the car and does a double take as he realizes it is on fire.
- I swear I did a double-take when I spotted that $100 bill lying in the gutter!
- Bulgarian: закъсняла реакция