A way of saying "one thicc boi". The "un" is the masculine indefinite article, meaning "a", from the Spanish language. "Thicc boi" is from the English language, and when combining these two phrases, makes a Spanglish sentence. This is a better way to say "one thicc boi" and is, from experience, more likely to get laughs. Sometimes you can say "un hella thicc boi" but that can be a bit over the top.
(Eighth graders learning about U.S. History)
Person 1: (whispers) Washington was un thicc boi, am I right?
Person 2: (Trying to muffle their laughter) Hell yeah!!!
Person 1: (whispers) Washington was un thicc boi, am I right?
Person 2: (Trying to muffle their laughter) Hell yeah!!!
by rootbeer&icecream May 4, 2018
Get the un thicc boimug. 
by Grass is thiccccccc June 25, 2019
Get the Thiccmug. Also commonly used as thicc to describe someones booty. Some thicc people are
Peter Hart and Nicholas Yasmeene
Peter Hart and Nicholas Yasmeene
by zappyvap October 10, 2018
Get the THICCmug. 
by PlumberwiththeG64 June 23, 2022
Get the Thicc hypemug.