[1] : The Collaborative International Dictionary of English v.0.48

impala \impa"la\, n.
   an antelope aepyceros melampus of southeastern africa,
   the male of which has ringed lyre-shaped horns, which curve
   first backward, then sideways, then upwards. also called
   impalla and pallah.
   pjc
see also:
aepyceros melampus impalla pallah 

[2] : The Collaborative International Dictionary of English v.0.48

impalla \impal"la\, n. zool.
   same as impala.
   1913 webster
see also:
impala 

Impalla >> I Words
Impalla, definition of term: Impalla
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