Adjective

(er)

Lacking in courage or confidence.

*{{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)

, chapter=19 citation , passage=When Timothy and Julia hurried up the staircase to the bedroom floor, where a considerable commotion was taking place, Tim took Barry Leach with him. […]. The captive made no resistance and came not only quietly but in a series of eager little rushes like a timid dog on a choke chain.}}

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.