Breadcrumb Home > Thesaurus > S Synonyms of sill Find synonyms for: Noun 1. sill, structural member usage: structural member consisting of a continuous horizontal timber forming the lowest member of a framework or supporting structure 2. sill, rock, stone usage: (geology) a flat (usually horizontal) mass of igneous rock between two layers of older sedimentary rock WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of sill (Dictionary) TrendingHere are the facts and trivia that people are buzzing about. Chinese New Year History, Meaning, and Celebrations Current Events This Week: February 2024 Valentine's Day Valentine's Day History Mardi Gras 30 "Charlie and the Chocolate Factory" Quotes ✖ Related Content Daily Word Quiz: apotheosis Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language