1. A person who is older in age. Often used as a term of address. Hey, old-timer—let me help you carry those! There are a few old-timers who come into the restaurant every morning like clockwork.

2. Someone who has a lot of experience in some activity, field, or profession (whether or not they are actually elderly). Often used as a term of address. I'm giving you a desk next to Martin. He's an old-timer in the company, and he'll help show you the ropes.