Other forms: guys
A guy is a man, spoken of casually. A nice guy, the guy at the counter, some guy called about the boiler.
In the plural it has gone further: you guys is used to address a group of any gender, and hey guys is one of the most common openings in English speech and video. Some people object to that on the grounds that it is a male word doing neutral work, and folks or everyone are the usual alternatives. Note that in Britain a guy is also the effigy burned on Bonfire Night, and that a guy rope on a tent is a different word entirely.
1nounguyA man, informally.
“Some guy in a van dropped it off.”
2nounpluralIn the plural, a group of people of any gender.
“Are you guys coming or not?”
3nouneffigyAn effigy burned on Bonfire Night.
“The children made a guy out of old clothes.”
Too few real examples of this word to estimate which sense is commonest.
guy is a man, informally.
The word is a person's name. Guy Fawkes was hanged for the Gunpowder Plot of 1605, effigies of him were burned each November and called guys, and the word slid from the effigy to a badly dressed man to any man at all — one of very few English common nouns made from a real individual.
Proto-Germanic
*widuz
Old Dutch
Wido
Proto-West Germanic
*Widō
Old French
Gui
English, today
guy
From Guy. Coined by semantic widening from the name of named after Guy Fawkes, an English Catholic executed for his role in the Gunpowder Plot, which also came to refer to effigies of his image burned annually on Guy Fawkes Night. The name Guy is from Old French Gui, from a Frankish - form of Proto-West Germanic Widō (compare Old Dutch Wido), a short form of names beginning with the element widu (“wood”), from Proto-Germanic widuz. Cognate with Italian Guido. a doublet of guido.
Etymology from Wiktionary, CC BY-SA