An awesome something or someone is amazing, breathtaking, or overwhelming. Like traveling the globe in a hot air balloon or visiting the Taj Mahal. Or, if you're 7, hearing someone burp the alphabet.
Awesome popped on the scene around 1600, probably in a church. It first meant “profoundly reverential,” but morphed later into an adjective meaning “inspiring awe.” Flash forward to the 20th century, when awesome transformed once again — this time into an everyday word for "impressive." These days it's synonymous with "outstanding" and "totally cool."