Part of speech: Adjective (satellite)
causing fear or dread or terror
Example: the awful war; an awful risk; dire news; a career or vengeance so direful that London was shocked; the dread presence of the headmaster; polio is no longer the dreaded disease it once was; a dreadful storm; a fearful howling; horrendous explosions shook the city; a terrible curse
Dread, Fearful, Awful, Dreaded, Frightening
The word "horrendous" was borrowed from Latin horrendus.
-ous – A related word in the same word family.
Roman military conquests permanently planted Latin vocabulary across three continents.