Any close family member or friend who routinely drinks a percentage of any beverage you have made for yourself without asking.
It never fails that when I open a new can of pop, my wife the drink invader waits until I walk away before she guzzles half the thing down.

I hate going to the bar with my friend Jill, she's a drink invader and it ends up costing me money because I buy twice as many drinks.
by Mr. Mensa September 25, 2007
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