A pub crawler is someone who visits multiple pubs in a single night. The term can be broken down into four parts: SOT (3 letters), ANT (3 letters), TOPER (5 letters), and BARFLY (6 letters). SOT stands for 'SOT', which is an old-fashioned word for a drunkard. ANT stands for 'ANTAGONIST', which is someone who opposes or competes with another. TOPER is derived from the word 'toping', which means to drink heavily. Finally, BARFLY is a combination of the words 'BAR' and 'FLY', which refers to someone who frequents bars. Therefore, a pub crawler is someone who visits multiple pubs in a single night, often drinking heavily and competing with others.