Use 'nondescript' to imply something doesn't stand out and is easily overlooked. The gallery was filled with nondescript artwork that I scarcely remembered.
Pro Tip 2/3
Not Negative
'Nondescript' doesn't have a negative connotation; it's neutral and factual. She drove a nondescript car, neither old nor new, that blended in with the rest.
Pro Tip 3/3
Visual Uniqueness
Often refers to the lack of distinctive visual characteristics. The spy chose a nondescript outfit to avoid drawing attention.