I. phrasal
1. : without further effort, argument, or consideration : as matters now stand
we'll let it go at that
2. : over and above what is expected or bargained for : besides
an interesting experience but a painful one at that
3. : even so : notwithstanding that
at that, you can still make a good profit
II. phrasal
1. : in spite of what has been said or implied : taking everything into consideration
we might be worse off at that
2. : in addition to what has already been said : into the bargain : besides
a bridge built on stilts, and weak stilts at that — O.S.Nock
3. : in the state or form indicated
we left it at that