Webster's Revised Unabridged Dictionary · 1913

Lackluster

Lackluster , noun

A lack of luster.

Also: Lacklustre

Lackluster , adjective

1.
Wanting luster or brightness.
Lackluster eye. — Shakespeare
2.
Lacking spirit, liveliness, or enthusiasm; dull.
3.
Mediocre; as, a lackluster performance.

Also: Lacklustre