Lewis & Short

trĕmesco (trĕmisco), ĕre, v. n. and a. inch. [tremo], to begin to shake or tremble, to shake, quake, or tremble for fear; to quake or tremble at a thing (poet.): plaustri concussa tremescunt Tecta viam propter, Lucr. 6, 548: tonitruque tremescunt Ardua terrarum, Verg. A. 5, 694: jubeo tremescere montes, Ov. M. 7, 205: latitans omnemque tremescens Ad strepitum, id. ib. 14, 214.
With acc.: sonitumque pedum vocemque tremesco, Verg. A. 3, 648: Phrygia arma, id. ib. 11, 403.
With object-clause: telum instare tremescit, Verg. A. 12, 916.
With rel.-clause: quercum nutantem nemus et mons ipse tremescit, Quā tellure cadat, Stat. Th. 9, 535.