Noun, Suru verb, Intransitive verb
diligent application (to work or study); cultivating one's character by studying hard
Yojijukugo (four character compound)
君の実力なら楽勝だとは思うが、それに驕らず、まずはクラスのみんなと切磋琢磨していって欲しい。I think you could easily win with your ability, but I want you to not be arrogant about it and work hard with everyone in your class first. mutual encouragement (to improve); working hard together; friendly rivalry
Yojijukugo (four character compound)
Also written 切瑳琢磨【せっさたくま】