Adjective

(en adjective)

Not secure.

Not comfortable or confident in oneself or in certain situations.

*{{quote-book, year=1963, author=(Margery Allingham)

, title=(The China Governess) , chapter=1 citation , passage=The half-dozen pieces […] were painted white and carved with festoons of flowers, birds and cupids. […]  The bed was the most extravagant piece.  Its graceful cane halftester rose high towards the cornice and was so festooned in carved white wood that the effect was positively insecure , as if the great couch were trimmed with icing sugar.}}

He's a nice guy and all, but seems to be rather insecure around other people.

Adjective

(en adjective)

Trembling, quivering, or shaking.

* 1850 , , The Scarlet Letter , ch. 3:

The trying nature of his position drove the blood from his cheek, and made his lips tremulous .

* 1919 , , A Man Four-Square , ch. 27:

"Thank God!" he cried brokenly, all the pent emotion of the long night vibrant in his tremulous voice.

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Timid, hesitant, or unconfident.

* 1891 , , The Great Taboo , ch. 15:

"You have lived here long?" Felix asked, with tremulous interest, as he took a seat.

* 2009 Oct. 7, , " Opinion: Gourmet to All That," New York Times (retrieved 18 Aug 2012):

This, hard on the heels of the death of Julia Child in 2004, makes one tremulous about the future.