Add to this list: Eldritch, rugose, squamous, non-Euclidian, nameless (in fact he usually ends up supplying a name for his nameless horrors). He likes certian phrases too: eg "rimed with nitre" (as opposed to "a bit white-ish").
Certan authors have a penchant for their favourite terms. E.E. "Doc" Smith gave the term "coruscating"" a real workout.
H.P. had a wide vocabulary as was not afraid to use it: in this he reflects the deliberate quaint archaizing of the late 19th century authors he so admired: its hard not to blame Dunsany for this.
edit-anyway, whats wrong with "Cyclopean"? Ain't you ever met anyone from Cyclopia before?
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