The Collaborative International Dictionary of English v.0.48:

Guava \Gua"va\, n. [Sp. guayaba the guava fruit, guayabo the
   guava tree; prob. fr. the native West Indian name.]
   A tropical tree, or its fruit, of the genus Psidium. Two
   varieties are well known, the P. pyriferum, or white
   guava, and P. pomiferum, or red guava. The fruit or
   berry is shaped like a pomegranate, but is much smaller. It
   is somewhat astringent, but makes a delicious jelly.
   [1913 Webster]

WordNet (r) 3.0 (2006):

guava
    n 1: small tropical shrubby tree bearing small yellowish fruit
         [syn: guava, strawberry guava, yellow cattley guava,
         Psidium littorale]
    2: small tropical American shrubby tree; widely cultivated in
       warm regions for its sweet globular yellow fruit [syn:
       guava, true guava, guava bush, Psidium guajava]
    3: tropical fruit having yellow skin and pink pulp; eaten fresh
       or used for e.g. jellies