Is unabridged an anapest?

Yes it is. Remember two short syllables folllowed by one long one.

Not really. An anapest is a 3 syllable foot with the first 2 unstressed, and the 3rd stressed. As in Lord Byron's "...and his cohorts were gleaming in purple and gold" and his CO horts were GLEA...

complete, entire, full-length, intact, total, unabbreviated, uncondensed, uncut, unexpurgated, unshortened, whole

No. An anapest has two short syllables followed by one long sylable. Hideous has a long first syllable followed by two short ones.

the unabridged dictionary lists more entries and often gives more definitions for a particular entry.