Similarly glossed in other lexica. Although the noun is attested only in lexicography, the stem ῥαπιδ- is implied by the verb ῥαπίζω (cf. rho 45, and the quotation at xi 46 = sigma 1264).
This is sense I in LSJ s.v.; note also senses II (a kind of shoe) and III (a kind of turnip) there, likewise unattested outside lexica.