LSJ Gloss:τελειωτήςan accomplisher, finisherDodson:τελειωτήςa perfecter, completera perfecter, completer, finisher.
TBESG:τελειωτήςfinisherG:N-M τελειωτής, -οῦ, ὁ (< τελειόω), a consummator, finisher: Heb.12:2 (nowhere else).† (AS)
Thayer:1) a perfector 2) one who has in his own person raised faith to its perfection and so set before us the highest example of faith
τελειόω teleioō tel-i-o'-o From G5046; to complete, that is, (literally) accomplish, or (figuratively) consummate (in character)KJV Usage: consecrate, finish, fulfil, (make) perfect.