Under these conditions, any sort of advance was impossibly slow and occasioned massive casualties.

Circulation growth inched up, but at an impossibly slow rate.

Progress seemed impossibly slow, but at last the city wall loomed ahead, filling the apparent sky.

Every lurch of his heart seemed impossibly slow; the gaps between the seconds were imponderable and vast.

Cerryl could feel the strain she was under, trying to deal with chaos and his impossibly slow reactions.

She knew an old trick, impossibly slow in ordinary free space.

It was impossibly slow and at the same time blindingly fast.

Anything done by word-level simple transmission of instructions would have been impossibly slow.

But by Act II, the conductor's tempos strike him as impossibly slow.

Sim's impossibly slow; he's dead if he doesn't improve.