The full form of oot is out of town.
The most commonly accepted meaning of the acronym “oot” or “OOT” means the phrase “out of town.”

Origin of OOT
The phrase “out of two” originated in 1944 because of a play that was produced in that same year. The phrase gained further popularity after a feature film was released based on the same play in 1949. Since this time, this phrase has been used in everyday conversation and speech to mean that someone is leaving town on vacation or for some other type of reason. With the popularity of text messaging and online chatting, many phrases that have been used for years were shortened to acronyms to save time typing messages out.

Other Meanings
There are many other possible meanings of this acronym. The official meaning of the word, not the acronym, according to the Miriam Webster Dictionary is the Scottish variant of saying the word “out.” The Urban Dictionary shows several other meanings of this term as an acronym and as a stand-alone word. As a word, it can mean a way to describe someone or something in a negative way or as an exclamation when recalling an awful experience. As an acronym, contributing users say it can also mean Ocriana of Time, referring to the Legend of Zelda game.

Example Conversations
Friend 1: Hey, do you think you could look after Benji for me this weekend?
Friend 2: Sure, where are you going?
Friend 1: Brian wants to go oot this weekend and he has asked me to go with him.
Friend 2: Aww! That’s sweet! I will watch him for you.