British slang. A pub crawl is where a group of people will try to visit as many pubs as possible in one night, having a set number of alcoholic beverages in each.
The most famous pub crawl is over the christmas holiday. The objective is to have one pint in each of 27 pubs that are nearest to each station on the distinctly beer-bottle shaped circuit.
An activity where at least 5 people are involved in drinking at a series of pubs, usually at least 4.
London's Ultimate Pub Crawl is the best known of said crawls.
Other examples are the Circle Line Pub Crawl and the Monopoly Board Pub Crawl.
Mate, that pub crawl was Ultimate!