hen's tooth(redirected from hens' tooth)
Something very scarce (because hens have no teeth). Typically used in phrases like "as scarce as a hen's tooth." I can hardly believe your brother got an A on his final exam—grades like that are as scarce as a hen's tooth for him!
See also: tooth
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.