The Collaborative International Dictionary of English v.0.48:

Gravity \Grav"i*ty\, n.; pl. Gravities. [L. gravitas, fr.
   gravis heavy; cf. F. gravit['e]. See Grave, a., Grief.]
   1. The state of having weight; beaviness; as, the gravity of
      lead.
      [1913 Webster]

   2. Sobriety of character or demeanor. "Men of gravity and
      learning." --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gravity
    n 1: (physics) the force of attraction between all masses in the
         universe; especially the attraction of the earth's mass for
         bodies near its surface; "the more remote the body the less
         the gravity"; "the gravitation between two bodies is
         proportional to the product of their masses and inversely
         proportional to the square of the distance between them";
         "gravitation cannot be held responsible for people falling
         in love"--Albert Einstein [syn: gravity, gravitation,
         gravitational attraction, gravitational force]
    2: a manner that is serious and solemn [syn: graveness,
       gravity, sobriety, soberness, somberness,
       sombreness]
    3: a solemn and dignified feeling [syn: gravity, solemnity]
       [ant: levity]