noun deliverance of a prisoner on security for his appearance at a day.
2. mainprise ·vt to suffer to go at large, on his finding sureties, or mainpernors, for his appearance at a day;
said of a prisoner.
3. mainprise ·noun a writ directed to the sheriff, commanding him to take sureties, called mainpernors, for the prisoner's appearance, and to let him go at large. this writ is now obsolete.