1. (

• diffident ,
• shy ,
• timid ,
• unsure ,

) lacking self-confidence; "stood in the doorway diffident and abashed"; "problems that call for bold not timid responses"; "a very unsure young man" ;

2. (

• uncertain ,
• unsure ,
• incertain

) lacking or indicating lack of confidence or assurance; "uncertain of his convictions"; "unsure of himself and his future"; "moving with uncertain (or unsure) steps"; "an uncertain smile"; "touched the ornaments with uncertain fingers" ;