The phrase "former manager" refers to a person who used to be in charge or responsible for a group of people or a particular job, but is no longer in that position. Full definition
Include recommendations from former managers, colleagues, customers, and vendors. (dummies.com)
To do this, you could quote former managers, colleagues, or vendors. (livecareer.com)
When choosing your 3 - 4 references, it's best to use former managers or supervisors with whom you had a good relationship and who evaluated your performance. (livecareer.com)