1) Aback 2) Unbeware 3) Unwares 1) At a disadvantage 2) Bad way to be caught 3) By surprise 4) Inadvertently 5) One way to be caught 6) Short 7) So as to surprise 8) Suddenly 9) Suddenly and unexpectedly 10) Unknowingly or inadvertently 11) Without forethought or plan 12) Without warning 
• (adv.) Without design or preparation; suddenly; without premeditation, unexpectedly.
[adv] - without forethought or plan 2. [adv] - suddenly and unexpectedly
adverb suddenly and unexpectedly; `rain caught them unawares`; `sorrow comes to all, and to the young it comes with bittered agony because it takes them unawares`- A.Lincoln
while not aware or conscious of a thing oneself; unknowingly or inadvertently. · without warning; by surprise; suddenly; unexpectedly: to come upon someone unawares.