What do you call a person who uses vulgar words too often? [closed]

Two adjectives come to my mind for a person who uses excessive foul language:

1) crass

having or showing no understanding of what is proper or acceptable; rude and insensitive (http://www.merriam-webster.com/dictionary/crass)

2) vulgar (as you used in the title of your own question)

not having or showing good manners, good taste, or politeness (http://www.merriam-webster.com/dictionary/vulgar)

Both of these suggestions are more reflective of the person's demeanor or temperament than the cursing itself, but I think they could be more colorful (pun intended) alternatives.

I hope this is helpful to you!

Two excellent choices exist. The first can be used as either an adjective or noun, in slightly different forms:

foulmouth, adj. and n.
B. n.
A foul-mouthed person.

["foulmouth, adj. and n.". OED Online. June 2016. Oxford University Press. http://www.oed.com/view/Entry/73916 (accessed August 21, 2016).]

The adjective 'foulmouth' is obsolete in that form. Instead, the current version is 'foulmouthed':

foul-mouthed, adj.
Of persons and their utterances: Using obscene, profane, or scurrilous language.

["foul-mouthed, adj.". OED Online. June 2016. Oxford University Press. http://www.oed.com/view/Entry/73917 (accessed August 21, 2016).]

The second choice is not so commonly used, and is only found as a noun. However, there's no mistaking its meaning:

muck-spout n. regional and slang a person who uses obscene or foul language.

["muck, n.1". OED Online. June 2016. Oxford University Press. http://www.oed.com/view/Entry/123164?redirectedFrom=muck-spout (accessed August 21, 2016).]

An alternative to @JEL's answer is the noun

potty-mouth

Dictionary.com. The Dictionary of American Slang. http://www.dictionary.com/browse/potty-mouth (accessed: August 21, 2016)

The corresponding adjective is

potty-mouthed : using or characterized by bad language.