Letters that make at once
a, o, e, n, c, t are letters that make 'at once'
2 possible definitions for 'at once'
Under this definition, at once is an adjective and has the following properties:
at a time, at one time have the same meaning as 'at once'
Under this definition, at once is an adjective and has the following properties:
straightaway, now, immediately, instantly, straight off, directly, right away, forthwith, like a shot have the same meaning as 'at once'
immediate pertains to 'at once'.