A sot is someone who frequently drinks too much alcohol. If you see someone stumbling out of a bar in the middle of the day, you might be tempted to describe him as a sot.
Sot is a somewhat old-fashioned word for a heavy drinker, also known as a lush or a wino. It's also considered insulting and derogatory. The character of the sot has featured in literature and film for years, going at least as far back as Shakespeare, whose famous sots included the drunken Falstaff in "Henry IV" and Sir Toby Belch in "Twelfth Night." In Old English, a sott was a "stupid person or a fool."