The headword -- presumably (though not demonstrably) extracted from the quotation given -- is present active infinitive of proskrou/w (literally, 'bash against'). For another form of the same verb see already pi 2723; and cf. the glossing noun at pi 2739.
[1] Procopius, History of the Wars of Justinian 7.16.19 (web address 1), here abridged (and transmitted, in Adler's view, via the Excerpta Constantini Porphyrogeniti). The quotation is taken from Totila's (cf. tau 879) address to Pelagius (cf. alpha 1585), upon the latter's appearance before the Gothic king to plead for relief from the siege of Rome (probably late 546 CE); cf. Kaldellis (412). Totila sharply reminds Pelagius that Theoderic (cf. theta 296)--complying with a Roman request to not burden the Sicilians--had left the island lightly garrisoned, only to have the local population welcome the invasion of Sicily by an overwhelming Byzantine force (in 535; cf. Bury (170-171)).