The Collaborative International Dictionary
Mainprise \Main"prise\, n. [F. main hand + prise a taking, fr. prendre, p. p. pris to take, fr. L. prehendere, prehensum.] (Law)
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.
--Wharton.Deliverance of a prisoner on security for his appearance at a day.
Mainprise \Main"prise\, v. t. [imp. & p. p. Mainprised; p. pr. & vb. n. Mainprising.] (Law) To suffer to go at large, on his finding sureties, or mainpernors, for his appearance at a day; -- said of a prisoner.
Wiktionary
n. 1 (context legal historical English) A writ directed to the sheriff, commanding him to take surety, called mainpernors, for the prisoner's appearance, and to let him go at large. 2 (context legal historical English) Deliverance of a prisoner on security for his appearance at a day. vb. (context transitive legal English) To allow (a prisoner) to go at large, on his finding surety, or mainpernors, for his appearance on a given day.
Wikipedia
Mainprise is a concept in English law regarding the release of a prisoner from custody upon sureties pending trial. It is nearly identical to the concept of bail and has been absorbed into the laws regulating bail in many jurisdictions. When they were distinguished, bail was not restricted in the type of surety upon which a prisoner could be released, while mainprise always involved a specified sum of money. A prisoner released on bail was still technically in custody and could be re-seized, while one delivered on mainprise was no longer in custody and could not have suits brought against him as though he were.
Usage examples of "mainprise".
And they shackled him hand and foot and would take of him ne bail ne mainprise but preferred a charge against him for he was a malefactor.
University, and still he had to find mainprise before he could be set free.