Is there a word to describe someone who often inaccurately uses words?

Solution 1:

The act of using a word inaccurately could be called catachresis. Catachresis is defined as: "the misuse or strained use of words, as in a mixed metaphor, occurring either in error or for rhetorical effect." Or as: "The use of a word in a way that is not correct, for example, the use of mitigate for militate.

It has the adjective form of catachrestic.

This entry in Wikipedia says catachresis can be either unintentional or intentional. It's a fun word to say. Just be sure YOU use it correctly.

Solution 2:

It's a malapropism and you may address the person who uses such as Mrs Malaprop.

Solution 3:

I think your description of this person requires two words:

1 "inaccurately using complicated or unusual words" = ignorant.

2 "in an attempt to sound more intelligent" = pompous, pretentious

Although bombastic, pompous, and pretentious are often synonymous, each has a different connotation and use. Of these three, I think that only pretentious implies the probability or possibility of ignorance and misuse of words. Pomposity and bombast imply overdramatization rather than deceit.