LSJ Gloss:ἀθλέωhaving contended withDodson:ἀθλέωI competeI engage, compete, in an (athletic) contest.
Strong's:ἀθλέω to contend in the competitive gamesDerivation: from ἄθλος (a contest in the public lists);KJV Usage: strive.
TBESG:ἀθλέωto competeG:V ἀθλέω, -ῶ (in cl. also ἀθλεύω, < ἆθλος, a contest, in war or in sport), to contend in games, wrestle, combat: 2Ti.2:5.† (AS)
ἀθλέω athleō ath-leh'-o From ἄθλος athlos (a contest in the public lists); to contend in the competitive gamesKJV Usage: strive.
συναθλέω sunathleō soon-ath-leh'-o From G4862 and G118; to wrestle in company with, that is, (figuratively) to seek jointlyKJV Usage: labour with, strive together for.