To be clumsy; to lack dexterity.

to get (a passing vehicle) to stop and give one a ride, signalling to the driver by holding out one's thumb (as a hitchhiker) / to disapprove or reject

plural of black thumb

A lack of skill in gardening; brown thumb. / (more generally) An inability to make animals or plants in one's care thrive. / A person with a black thumb.

plural of thunder-plump

(archaic) A heavy fall of rain in a thunderstorm.

(historical) To express defiance by putting one's thumbnail into one's mouth and knocking it against the teeth.

plural of Thucydidean

(idiomatic) An adventure or active endeavor that is characterized by (often humorous) errors.

(South Africa, transitive, informal) To make up, to fabricate, to pull out of one's ass.