Transom/ˈtrænsəm/ Definition 1 of 3Pro Tip 1/2Architectural Element Remember 'transom' as an architectural feature, usually decorative, above doors or windows. The old mansion had a transom with intricate carvings. Pro Tip 2/2Not Always Functional A transom can be purely decorative and may not always serve a practical purpose. Their house has a faux transom purely for aesthetic appeal.