Lewis & Short

trĕbax, ācis, adj. [contr. from the Gr. τριβακός], practised, skilled in the ways of the world, cunning, crafty (lat. Lat.): trebacissimus senex, Sid. Ep. 1, 11 med.
Adv.:
trĕbācĭter, cunningly, slyly, Sid. Ep. 9, 11 med.