a (physics) of a value divided by mass (e.g. specific orbital energy)
a (physics) similarly referring to a value divided by any measure which acts to standardize it (e.g. thrust specific fuel consumption, referring to fuel consumption divided by thrust)
a (physics) a measure compared with a standard reference value by division, to produce a ratio without unit or dimension (e.g. specific refractive index is a pure number, and is relative to that of air)