— subbasal , adj.
/sub"bays'/ , n.
1. Archit. the lowest part of a base, as of a column, that consists of two or more horizontal members.
2. Math. a collection of subsets of a topological space having the property that every open set of a given topology can be written as the union of intersections of finite numbers of sets in the collection. Cf. base 1 (def. 13b).
[ 1820-30; SUB- + BASE 1 ]