1. [n]  a barometer that measures pressure without using fluids
2. [adj]  containing no liquid or actuated without the use of liquid; "aneroid barometer"

ANEROID is a 7 letter word that starts with A.

1. \An"e*roid\, a. [Gr. 'a priv. + nhro`s wet, moist +
   -oid: cf. F. an['e]ro["i]de.]
   Containing no liquid; -- said of a kind of barometer.
   
   {Aneroid barometer}, a barometer the action of which depends
      on the varying pressure of the atmosphere upon the elastic
      top of a metallic box (shaped like a watch) from which the
      air has been exhausted. An index shows the variation of
      pressure.
   
   

2. \An"e*roid\, n.
   An aneroid barometer.