Weatherstrip: a flexible component used to reduce air leakage, water penetration, or both between sash, leaf, panel, and/or frame.

Water penetration: penetration of water beyond the plane intersecting the innermost projection of the test specimen, not including interior trim and hardware, under the specified conditions of air pressure difference across the specimen.

Weep-hole:  an opening that allows water to drain.

Welded: when materials are fused by heat to become one when cooled.

Wire Glass: glazing that is produced by overlaying electrically welded, chemically treated, steel wire mesh over molten glass as it begins the controlled cooling process.

Window: a glazed opening in an external wall of a building; an entire unit consisting of a frame sash and glazing, and any operable elements.

Warm-edge technology: The use of low-conductance spacers to reduce heat transfer near the edge of insulated glazing.