horrent
Standing upright, like bristles; bristled; bristly.
Impregnable their front appears, All horrent with projected spears, Whose polished points before them shine, From flank to flank, one brilliant line, Bright as the breakers' splendors run Along the billows to the sun.
Where it comes from
From Latin horrens, present participle of horrere (“to bristle”). See horror.
Adapted from the Wiktionary entry horrent (CC BY-SA 4.0).