(chiefly attributive) Anything ingenious (and often complex) but absurdly impractical or even useless.

Of or pertaining to bone marrow. / (less commonly used) Of or pertaining to the spinal cord.

Not able to be passed. / (tennis) Not able to be passed; not capable of being beaten at the net by a passing shot. / (LGBT) Unable to pass successfully as the gender one wishes to be seen as.

A person who overnights, or stays overnight. / Something that serves overnight travel, such as a night train. / (informal) A stay or event that takes place overnight.