B1
an extra amount of money that you give to a driver, someone working in a restaurant, etc to thank them
Dictionary examples:
The taxi driver's eyes lit up when he saw the generous tip. (0.0)
The waiter juggled plates, hoping for a big tip, not a standing ovation. (0.0)
The tour guide's tip was so big, he could afford a vacation himself. (0.0)
Have you left a tip for the waiter? (18.6)
a 15% tip (21.5)
He gave the porter a tip. (51.0)