Idby 

This has two meanings. It can mean "I don't believe you" or "I don't blame you". Just the same abbreviations.

Max: I just met a celebrity 5 minutes ago!!
Sam: Really? No, bruh... Idby (I don't believe you.)

Or

Max: I'm very worried about my girlfriend. she hasn't texted me in days.

Sam: I would be worried too. Idby (I don't blame you)

Idby by Black Dwarf Bunny January 20, 2018

idby 

I dont believe you, often used in text or internet language among young people.

John: I'm going to America tomorrow to eat in McDonald's.
Patrick: idby!

idby by eefa January 10, 2008

Idby 

An acronym for "I don't blame you."

Person 1: "I'm thinking about dropping AP Chem."
Person 2: "That class is way too hard anyways, idby."

Idby by I'm a potato August 2, 2019

idbyou 

I Don't Believe You; used easily in Instant messaging conversations. But when spoken it is IDBY.

SAM: dude last weekend i got totally wasted and don't know what happened
J.R.: idbyou
SAM: whatever jerk

idbyou by DBAS March 30, 2008