Flimsy (adjective)

1. Lacking strength or solidity; easily broken, bent, or cut.
2. Lacking substance or significance; weak.
3. Lacking in substance or soundness; not convincing.

Origin:

Middle english, from flim flam + -y.

Examples:

1. The flimsy cardboard box fell apart as soon as I picked it up.
2. The flimsy excuse he gave was not convincing at all.
3. The flimsy argument she presented in court was easily refuted by the opposing lawyer.
4. The flimsy tent was not able to withstand the windy conditions.
5. The flimsy construction of the bridge made it dangerous to cross.