Sap - (Webster's 1828 Dictionary)
1. The juice of plants of any kind, which flows chiefly between the wood and the bark. From the sap of a species of maple, is made sugar of a good quality by evaporation.
2. The alburnum of a tree; the exterior part of the wood, next to the bark. [A sense in general use in New England.]
1. To undermine; to subvert by digging or wearing away; to mine.
Their dwellings were sapp'd by floods.
2. To undermine; to subvert by removing the foundation of. Discontent saps the foundation of happiness. Intrigue and corruption sap the constitution of a free government.
SAP, v.i. To proceed by mining, or by secretly undermining.
Both assaults are carried on by sapping.
SAP, n. In sieges, a trench for undermining; or an approach made to a fortified place by digging or under cover. The single sap has only a single parapet; the double has one on each side, and the flying is made with gabions, _c. In all saps, traverses are left to cover the men.