The definition of tremulous is quivering, timid or nervous.(adjective)
When you give a quivering and uncertain smile because you are nervous, this is an example of a smile that would be described as tremulous.
See tremulous in Webster's New World College Dictionary
Origin: L tremulus < tremere, to tremble
See tremulous in American Heritage Dictionary 4
Origin: From Latin tremulus
Origin: , from tremere, to tremble.
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