I asked my dad about this term, as he is a reader in restorative dentistry at the University of Birmingham. He began by explaining that a general term for removal of gum tissue overlying unerupted teeth is "exposure" or "surgical exposure". However, this refers to the removal of gum tissue from a tooth which is completely covered by gingival tissue (i.e. when the tooth is completely "buried"), and it can refer to any kind of tooth, including canines, for example.

More specifically, "operculectomy" refers to removal of the operculum, which is a small flap of gum tissue that covers the crown of a partially erupted tooth, especially a wisdom tooth (it literally means "little lid" in Latin, just as "capuşon" in Romanian literally means "hood").

Decapusonare - metoda chirurgicala folosita in excizia fibromucoasei ce acopera coroana molarului, pentru a crea posibilitatea continuarii si reusitei eruptiei;
http://www.dentexsteph.ro/dictionary/Egresiune dentara.html

decapisonare laser (tratament de urgenţă stomatologică)
îndepărtarea gingiei crescute deasupra dintelui neerupt integral
http://www.exist.ro/laserdent/ro/packets.html

dental operculum
the hood of gingival tissue overlying the crown of an erupting tooth
http://medical-dictionary.thefreedictionary.com/operculum

OPERCULECTOMY - removal of the operculum
OPERCULUM - the flap of tissue over an unerupted or partially erupted tooth
http://www.smilesandiego.com/glossary.html

See also the following link, which gives a detailed explanation plus some pictures:

Operculectomy/Excision of pericoronal gingiva

Sometimes the back molars come in and the gum tissue over them is thick and does not recede out of the way, as normally occurs. Closing the teeth together, eating, etc., can be difficult and painful. Food also has a habit of getting stuck under the flap of gum tissue. The infections that result (pericoronitis) can be painful, as the swelling makes it impossible to close the teeth together and chew food without causing the opposing tooth to "chew" into the swollen gum. Most patients we see with this are in their early teens. If the tissue overlying the tooth is small, it is called an operculum, and its removal is referred to as an operculectomy. If the tissue is large, it is referred to as pericoronal gingiva, and its removal is referred to as excision of pericoronal gingiva.
http://www.fwperio.com/procedures.asp