Definition: Exoteric means "Intended to be understood by the general public"; it is more or less the antonym of the much more common word esoteric. Ironically, exoteric itself is not very exoteric, since few people know what it means!
Origin: Exoteric comes from the Latin exotericus meaning "external, belonging to the outside world" which in turn comes from Greek exoterikus with the same meaning.
Pronunciation: Ex oh tehr eh kus
Why use it? It's a good descriptive word for popularized science and other technical fields. Exoteric can also be used sarcastically.
Examples: "Neil deGrasse Tyson is well known for his exoteric talks on astronomy and other subjects".
"Although she intended her talk to be exoteric, in reality, almost no one understood her".
"Shakespeare's plays were originally exoteric, but changes in the language have rendered them less so over time".