Flimsy and Weak-kneed

Flimsy adjective - Being of a material lacking in sturdiness or substance.

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

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

Flimsy and weak-kneed are semantically related in deficient topic. Sometimes you can use "Flimsy" instead an adjective phrase "Weak-kneed".