Of or pertaining to the Hilary in your life. May indicate ownership or reference to an idiosyncrasy pertaining to the Hilary-person:
1. Indicating ownership:
Person 1: "Oh my gosh, that sweater is Hilaryous!"
Person 2: "Oh, okay, I was wondering to whom it belonged. Hilary must have left it here, the last time she visited."

2. Pertaining to idiosyncrasy of the Hilary-person:
Person 1: "You know that thing Hilary always does, when she leaves social gatherings without notifying her friends? She seems to catch a thrill from gaining MIA status; it happens nearly every weekend."
Person 2: "Oh yes, that thing. It's never funny but so Hilaryous all the same."
by Anna Kingsley December 16, 2013
when something is so hideous it makes you laugh.
Hilary Clinton is hilaryous!
by Amy Jellybeater August 1, 2008
When something that Hilary Clinton says is suxh bs that it's hilarious.
When Hilary vote for the war in Iraq it was hilaryous.
by Memestealingwhore October 10, 2016