v. 1
To puzzle, perplex, baffle, bewilder (somebody); to afflict by being complicated, contradictory, or otherwise difficult to understand.
It confused me when I went to the office and nobody was there, but then I realised it was Sunday.
v. 2
To mix up, muddle up (one thing with another); to mistake (one thing for another).
People who say "hola" to Italians are confusing Italian with Spanish.
v. 3
To mix thoroughly; to confound; to disorder.
The dense fog utterly confused traffic on the highway.

Related words

Forms

Past participle: confused
e.g. confused → confounded, befuddled, bewildered, perplexed…

befuddle In the event that you can't persuade them, befuddle them.
disconcert I don't mean to disconcert you, but there's a spider in your hair.
mistake If that man makes one more mistake, I'll fire him.

Use in printed books, per decade from 1850 to 2019.

3 letters: get¹, fog¹
4 letters: blur¹
5 letters: throw¹
6 letters: rattle², flurry², dazzle², darken², muddle², jumble², baffle², masker², fuddle²
7 letters: mistake², obscure², disturb², agitate³, perplex², mystify³, fluster², bedevil³, embroil²
8 letters: distract², confound², unsettle³, entangle³, bewilder³, befuddle³
9 letters: embarrass³, obfuscate³, ambiguate
10 letters: complicate³, disconcert³, obnubilate

The small number after each word is its number of syllables (rattle² = 2 syllables).