1.
unknown, obscure, nameless
Not famous or well-known. Used to describe people, places, or things that have not gained recognition or fame.
2.
anonymous
Having no name attached, or the identity is not known or disclosed.
Common patterns
Used as a noun (無名) and as a no-adjective modifier (無名の).
Similar words
無名 (unknown/nameless) is the opposite of 有名 (famous). The pair 無名/有名 shares the same structure: 無/有 (without/with) + 名 (name/fame).
Watch out
An unsigned Japanese sword, one with no swordsmith's inscription (銘) on the tang, is 無銘, a different word with the same reading; 無名 is not the sword term.