To get drunk or start drinking before the hang over from last night has worn off.

Thus having something to "tie onto"

To tie one drinking session to another before the effects/consequences of the last have expired.
Guy 1: Hey, what's going on there?
Guy 2: I'm hungover as fuck, they had quarter pitcher night at Jake's last night.
Guy 1: So you're just going to hang out?
Guy 2: Fuck it lets tie one on.
Guy 1&2: *Crack open beers and commence drinking*
by QWERTY1 April 19, 2006
To get drunk.

It is thought that its origin dates back to the wild west in the 1800's, where a cowboy would have to tie up his horse to a hitching post before he could go into the saloon and get drunk.

A British slang for this term, "tie a bun on", also means "to get drunk", however nobody is quite sure how someone came up with that one...
Trying to figure out the meaning behind these slangs is making my head hurt...and driving me to tie one on.
by ItsBeenReal October 7, 2009
get drunk for purpose of getting drunk
"when this is over I'm going to tie one on"
by Anonymous August 10, 2003
To drink with the intention of becoming intoxicated, as opposed for purely social reasons.
One will often tie one on when looking to have a good time or self-sooth

So do this thing with me
Instead of tying on a tight one tonight
~Interpol, Nex Exit
by L Cali November 25, 2005
Indulge in consumption of alcoholic beverages; probably until physical impairment sets in.
I got sacked today - fuck it, I'm gonna tie one on
by notapaki August 10, 2003
To get drunk, sauced, hammered, sleighed, intoxicated, snookered, pissed, sh!t faced or wasted.
I tie one on and called some chick I met on the internet.
by Drew & Marguerite May 11, 2008