SAP, noun

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.]

SAP, verb transitive

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, verb intransitive To proceed by mining, or by secretly undermining.

Both assaults are carried on by sapping.

SAP, noun 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, etc. In all saps, traverses are left to cover the men.