UPPERMOST

[adjective], [adverb] [not gradable]The office block's uppermost floors (= those in the highest position) were engulfed with flames.Store the canisters with their lids uppermost (= in the highest position).If environmental considerations are uppermost (= most important), then energy efficiency measures must take priority over profitability.What's uppermost in your mind (= the most important thing you are thinking about) just before a race when you're waiting for the starter's signal?