na-adjective, noun
poor; meager; feeble; shabby; insubstantial
Describes something lacking in quantity, quality, strength, or substance. Can refer to physical build, content, resources, arguments, etc.
彼の提案は内容が貧弱だった。
His proposal was insubstantial in content.
貧弱な体格の少年が立っていた。
A boy with a feeble build was standing there.