Definify.com

Webster 1913 Edition

Adj.

Apt to suspect or mistrust; full of suspicion; suspicious;

as, to be

suspectful

of the motives of others

Milton.

–

Sus-pect′ful-ness

Noun.

Adj.

Apt to suspect or mistrust.

suspectful ‎(comparative more suspectful, superlative most suspectful)

(now rare) Mistrustful, suspicious.
- 1644, John Milton, Aeropagitica:
  Whence to include the whole Nation, and those that never yet thus offended, under such a diffident and suspectfull prohibition, may plainly be understood what a disparagement it is.