shield; buckler
Literal protective shield used in combat or historical contexts.
騎士は左手に盾を持っていた。
The knight held a shield in his left hand.
pretext; excuse; justification
Figurative use: something used as a cover or justification for an action, often in the phrase 盾に取る (to use as a pretext).
See also: 盾に取る
彼は病気を盾に欠席した。
He used illness as an excuse to be absent.
法律を盾に取って反論する。
To argue back using the law as a shield.
He used his busyness as an excuse not to help.
The soldier raised his shield to block the enemy's attack.
He made unreasonable demands, using his boss's authority as cover.