It could be a misspelling or an uncommon term.
To figure out the pronunciation, you need more context:
* What is the word's origin? Is it a technical term, a foreign word, or a made-up word?
* What is the surrounding text? The context might provide clues about the pronunciation.
Possible Pronunciations (based on possible spellings):
* Co-err: Pronounced like "co-air"
* Coer: Pronounced like "core"
* Co-err: Pronounced like "co-er"
If you provide more information about the word and its usage, I might be able to give you a more accurate pronunciation.