• to be at a loss to understand
• I am at a loss to understand
• he can't hide his amusement
• absurdity, bushwa, inability, incapacitation, incapacity, incongruence, incongruity, nonsense, ridiculousness
• to disable, to incapacitate
• disablement, incapacity
• bankruptcy, default, insolvency
• plumb nonsense, sheer nonsense