a. 无懈可击的, 极好的, 完美无缺的

[ adj ]
completely acceptable; not open to exception or reproach
<adj.all>
two unexceptionable witnessesa judge's ethics should be unexceptionable

Unexceptionable \Un`ex*cep"tion*a*ble\, a.
Not liable to any exception or objection; unobjectionable;
faultless; good; excellent; as, a man of most unexceptionable
character. -- {Un`ex*cep"tion*a*ble*ness}, n. --
{Un`ex*cep"tion*a*bly}, adv.

Chesterfield is an unexceptionable witness. --Macaulay.