What it means
It means heading out for a proper drinking session and fully binning off the idea of taking it easy. If you're on the lash, this isn't a quiet pint and home by ten. It's a big night, too many rounds, bad maths at the bar, and tomorrow's head turning up with revenge in its heart.
Usage examples
"Are we on the lash Friday? We’ll meet for one in town, and next thing it’s 3am at the chipper with a kebab and a raging hangover incoming."
"The whole team went on the lash after winning the final."
"I am off the lash this month, doing dry January properly."
"We’re on the lash after payday, so don’t expect any sensible decisions past eight."
"They went on the lash in Dublin and turned up the next morning looking like sleep had personally betrayed them."
Where it comes from
This is established British and Irish slang. By the mid 20th century, go on the lash was already being used for going out on a heavy drinking spree. In this sense, lash is tied to knocking drinks back hard, so the phrase points to a full-on session, not just having a casual pint.
Other ways to say it
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