unsubstantiated; flimsy; weakly grounded
Describes claims, arguments, or evidence that lack solid support. Often used in formal or critical contexts.
The accusation was unsubstantiated and had no evidence at all.
His argument was criticized as flimsy.
根拠 means 'grounds' or 'basis'; 根拠薄弱 is the adjectival form meaning 'lacking solid grounds'.
薄弱 means 'weakness' or 'feebleness'; it combines with 根拠 to specify weakness of evidence or reasoning.
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.