Sentence:  Suddenly a treble auto horn tootley-toot-tootled , and , thumbing hopefully , I saw emergent in windshield flash : red lips , streaming silk of blonde hair and - ah , <WSD>trembling</WSD> confusion of hope , apprehension , despair - the leering face of old Herry . 
Meaning of the word marked with <WSD> tags:  vibrating slightly and irregularly; as e.g. with fear or cold or like the leaves of an aspen in a breeze