na-adjective
unsubstantiated; flimsy; weakly grounded
Describes claims, arguments, or evidence that lack solid support. Often used in formal or critical contexts.
その告発は根拠薄弱で、証拠がまったくなかった。
The accusation was unsubstantiated and had no evidence at all.
彼の主張は根拠薄弱だと批判された。
His argument was criticized as flimsy.
Compound of 根拠 (grounds, basis) and 薄弱 (weak, feeble). The exact historical derivation is uncertain, but the word follows standard Sino-Japanese compounding patterns.