v. phr. To depend on something that is useless or unable to help in a time of trouble or danger; try something with little hope of succeeding. To depend on your memory without studying for a test is to grasp at straws. The robber clutched at straws to make excuses. He said he wasn't in the country when the robbery happened.
GRASP AT STRAWS
Meaning of GRASP AT STRAWS in English
American idioms English vocabulary. Английский словарь американских идиом. 2012