ephebe
Concise Oxford English Dictionary © 2008 Oxford University Press:
ephebe /ɛˈfiːb, ɪ-, ˈɛfiːb/
▶noun (in ancient Greece) a young man of 18–20 years undergoing military training.
– derivatives
ephebic adjective.
ephebic adjective.
– origin via L. from Gk ephēbos, from epi ‘near to’ + hēbē ‘early manhood’.
'ephebe' also found in these Oxford entries:

