sapping
verb(sap)
to drain or deprive of sap
sapping
verb(sap)
to knock out with a sap
sapping
verb(sap)
to proceed by digging a sap
sapping
verb(sap)
to subvert by digging or eroding the substratum or foundation : undermine
sapping
verb(sap)
to gradually diminish the supply or intensity of