HEMISPHERIC is a 11 letter word that starts with H.
Webster's 1913 Dictionary
Definition:
\Hem`i*spher"ic\, Hemispherical \Hem`i*spher"ic*al\,
a. [Cf. F. h['e]misph['e]rique.]
Containing, or pertaining to, a hemisphere; as, a hemispheric
figure or form; a hemispherical body.
WordNet Dictionary