Lusterless and Weak-kneed

Lusterless adjective - Lacking a surface luster or gloss.

Weak-kneed and lusterless are semantically related. In some cases you can use "Weak-kneed" instead an adjective "Lusterless".

Weak-kneed adjective - Lacking strength of will or character.

Lusterless and weak-kneed are semantically related. Sometimes you can use "Lusterless" instead an adjective phrase "Weak-kneed".