You can use the word mess after someone says or does something that's embarrassing, stupid, pathetic, ridiculous, or weird. Honestly can be used after a lot of things. Even sometimes when you don't know what to reply, "mess" might work.
It's so hard to define mess... Mess. Check examples for a better understanding.
Sometimes has a t at the end. (Messt)

When someone is really funny

A person whose life has fallen into disrepair. Or one who is suffering the effects of intoxicating substances, perhaps on a prolonged basis.

An overly clumsy person who seems to have no control over his/her body.

to engage in an act of self pleasure

1. to hang out with a person with the intention of getting together and/or date. Term used in the south.

2. to be involved in the period before dating a person.

Someone who:
1. Gets ridiculously drunk
2. Gets themselves into awkward situations
3. Becomes clumsy, often spilling drinks, breaking things, being sick everywhere
6. Sleeps for the next two days to wear off the amount of drink drunk.

Often does this on a regular occassion, sometimes earning the title "mess of the month".

People sometimes come together to create a "mess chart" depending on how lazy/how much of a mess the person is