Sherlock, Get off with someone

Sherlock, Series 01, Episode 02, The blind banker.


Sherlock: All I need to do is have a quick look around the place

Dr. Watson: Fine. You do that, I'll take Sarah for a pint.

Sherlock: I need your help

Dr. Watson: I do have a couple of other things on my mind this evening.
Sherlock: Like what?

Dr. Watson: You are kidding? What's so important? Sherlock, I'm right in the middle of a date. You're going to chase some killer while I'm trying to...

Sherlock: What?

Dr. Watson: While I'm trying to get off with Sarah. Hey... Ready?

Sarah: Yeah.

To get off with someone: to start a sexual relationship with someone