look up any word, like cleveland steamer:
 
1.
how uneducated people spell fool-proof.
despite any arguments for the validity of the word "fullproof" the correct spelling literally means 'even a fool couldn't get this wrong'.
clearly the spelling of the word fool-proof is not fool-proof.
Person 1: "It's a fullproof plan"

Person 2: "you're a fool."
by EducatedPerson February 27, 2012
 
2.
Complete evidence or argument for the truth of a proposition. Not to be confused with "foolproof."
(on Facebook)
John: Your plan to create a seagull army is ridiculous...
Sarah: No it's not! It's fullproof!
John: It's foolproof... and that's fullproof evidence that it's not, bitch.
by Matt73 March 14, 2012
 
3.
complete, absolute and total evidence or argument for the truth of a proposition.

I Information which tends to determine or demonstrate the truth of a proposition to full extent.

mathematical calculation that shows proof in absolute terms.
The prosecutor presented fullproof evidence against defendant in the murder case.

The scientific research results provided fullproof evidence to the existence of water in other planets

Professor with his Mathematically precise conception and logically efficient execution showed fullproof solution to the problem
by quixotic123 November 26, 2010