My own definition: for every e>0, there exists some d>0 such that for x < a and |x - a| < d, the following holds: f(x) < -e. You may prefer to write f(x) < -1/e, though it doesn't matter.
Another definition: for any convergent sequence {x_n} tending to a where each x_n < a, we have
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My own definition: for every e>0, there exists some d>0 such that for x < a and |x - a| < d, the following holds: f(x) < -e. You may prefer to write f(x) < -1/e, though it doesn't matter.
Another definition: for any convergent sequence {x_n} tending to a where each x_n < a, we have
lim n->inf of f(x_n) = -inf
where this limit is defined as usual.