An adjunct is something less important that is joined with something else.
For her, beauty was an undoubted adjunct to her ability to move from one opportunity of employment up to another. ^[1]
(countable) An adjunct is a professor who is not in a tenure-track position.
Nationwide, salaries for full-time faculty held up well, but major shifts were underway replacing regular tenure-track faculty with adjuncts or other cost-saving devices (bigger classes, more teaching hours, using technology to reach more people). ^[2]
(linguistics) (grammar) An adjunct is a modifier or supplement.
In the sentence he arrived last week, last week functions as an adjunct.

Noun

Adjective