Severely, sternly, harshly. Of punishment, discipline, etc. Now rare.

In extended use (chiefly with other types of verb), in which fast is characterized as much by its… With verbs of command or prohibition: urgently…

With reference to punishment, judgement, etc.: Rigorously, unsparingly, severely. Obsolete.

With rigour or extreme strictness in the treatment of offenders; with severity in judgement, punishment, censure or rebuke.

Sharply, severely, smartly.

quasi-adv.= severely, adv.

With reference to punishment, judgement, rule, etc.: Rigorously, unsparingly, severely.