black thumb noun3 •A lack of skill in gardening; brown thumb.I think of doctors as having the equivalent of green thumbs or black thumbs in gardening. — 2007 •An inability to make animals or plants in one's care thrive.In the interest of full disclosure, I am not now and never have been a big fan of keeping reptiles as pets; I have a “black thumb” when it comes to keeping animals alive in captivity. — 2013 •A person with a black thumb."Why?" She smiled. "Especially on family occasions like this, he feels he's been something of a black thumb in the Garden of Life." — 1966 formsblack thumbs
