Definition of "jittery"

Those were all landmark moments to cherish. Just as appealing was the manner in which Alex Oxlade-Chamberlain and Milner cut swathes down either flank, albeit through flustered full-backs who had looked poorly positioned and horribly jittery from the start.

2012 September 7, Dominic Fifield, “England start World Cup campaign with five-goal romp against Moldova”, in The Guardian‎