
Generally, to cause a reed to jump an octave by increasing the pressure on it. Some types of bagpipe, particularly the Uilleann pipe, require this technique to achieve the full range of the chanter.
Found on
http://en.wikipedia.org/wiki/Glossary_of_bagpipe_terms

• (v. t.) To blow away; to dissipate by wind, or as by wind. • (v. i.) To force so much wind into a pipe that it produces an overtone, or a note higher than the natural note; thus, the upper octaves of a flute are produced by overblowing. • (v. i.) To blow over, or be subdued.
Found on
http://thinkexist.com/dictionary/meaning/overblow/
O`ver·blow' intransitive verb 1. To blow over, or be subdued. [ R.]
Spenser. 2. (Mus.) To force so much wind into a pipe that it produces an overtone, or a note higher than the natural note; thus, the upper octaves of a flute are produced by
overblowing .
Found on
http://www.encyclo.co.uk/webster/O/49
No exact match found.