Literally: cut – scrub/rub – strike – polish/scour/grind
(or: cut – polish – polish – polish!)
Alternately: Diligent effort. Improving oneself through study.
Notes: There’s a fuller phrase, 切磋琢磨し合う (sessa-takuma shiau). The shiau part means “to do together,” “to do reciprocally.” This phrase, then, refers to people working hard together – often encouraging each other to greater efforts through friendly rivalry, like members of the same sports team. By extension, the same meaning can be contained in the original yojijukugo.