The following (slightly edited) quote from
Original Letters, Illustrative of English History: 1400-1526 edited by Henry Ellis:
is placed here to provide easy access to a definition which is missing from the Shorter Oxford English Dictionary and also from all lesser dictionaries that have been checked.
Kyng BESECHITH mekely youre poure liegeman and humble horatour Thomas Hostell that in consideration of his service doon to your noble progenitours of ful blessid memory Kyng Henrj the iiijtn and Kyng Henri the fift whoos soules God assoille being at the Siege of Harflewe there smyten with a springolt* through the hede lesing his oon ye^ and his cheke boon broken
*The springolt was a dart thrown from the Espringal and had brass plates instead of feathers to make its flight steady.