What is the word for pretending expertise?

Answer 1

a know it all :)

a charlatan

Assuming a person pretends to be something they aren't, or to know things they don't, simply to impress others or to make themselves feel important, nouns applicable to them include:

know-it-all

poseur (or poser)

pretender

pretentious (adjective)

pseud

show-off

If the person pretends specialist qualifications, knowledge or expertise or otherwise falsifies their history with the deliberate intention of obtaining some material gain to which they aren't entitled, nouns applicable to them them include:

charlatan

cheat

con-artist

confidence trickster

fake (or faker)

fraud (or fraudster)

hoaxer

imposter

quack (usually applied to people posing as a health professional)

scammer

swindler

trickster