The headword is a middle/passive infinitive apparently from the verb r(w/nnumi "I strengthen" (cf. rho 252, rho 263, rho 266) or perhaps from r(w/omai "I move with speed." This form is attested only in lexicography (Hesychius rho588, Photius rho213 Theodorides). An infinitive r(w/esqai, presumably from r(w/omai, is also found in Hesychius (rho560), with the gloss speu/dein, o(rma=n "to hurry, to rush." It is possible that r(w/nnumi and r(w/omai are etymologically related.
[1] The gloss is the present active infinitive of the verb spouda/zw, I make haste, I do (something) eagerly; see generally LSJ s.v. The same gloss is found in Hesychius and Photius.