Does a former coworker count as an employer when filling out a job application?

I thought I’d asked this question before but I couldn’t find it. I thought the answer then was that a coworker is OK to use as a reference, but I can’t remember! Just want to be sure.

Filling out a job ap. Instructions for references read:

PERSONAL REFERENCES: Give names and addresses of at least two persons, such as physician, lawyer, teacher,
minister, friends, etc. who can vouch for you personally (no relatives or employers).

Would it still be OK to use a former coworker?