from merriam webster

Main Entry: ath·lete
Pronunciation: 'ath-"lEt, ÷'a-th&-"lEt
Function: noun
Etymology: Middle English, from Latin athleta, from Greek athlEtEs, from athlein to contend for a prize, from athlon prize, contest
: a person who is trained or skilled in exercises, sports, or games requiring physical strength, agility, or stamina

IMO, if ride just to ride your a cyclist. if you ride to train, your not only a cyclist but an athlete.