Awesome means extremely impressive or, informally, very good. An awesome sight, that's awesome, awesome power.
It has weakened enormously: the older sense is something that inspires awe, which is closer to terror than to approval, and the everyday American sense means nice. Awful went the same way in the other direction, from awe-inspiring to bad. Note awe, which both are built on.
1adjectiveawesomeExtremely impressive.
“The awesome power of the waterfall made the ground shake beneath our feet.”
synonyms: awe-inspiring, magnificent
2adjectivegoodVery good, informally.
“"I got us tickets for the concert!" "Awesome, thanks!"”
awesome is a quality of impressiveness.
Awe plus -some. Awe comes from Old Norse agi, terror. Awful was formed the same way and went the other way in meaning.
Proto-Indo-European
*h₂egʰ- — to be upset, afraid
Proto-Germanic
*agaz — terror, dread
Old Norse
agi
Middle English
aw
English
awe
English, today
awesome
Built from
From awe + some; compare earlier awful and Middle English eifulle (“inducing fright or terror, terrible”), from Old English eġeful (“fearful; inspiring awe”). The oldest meaning of awesome is of “something which inspires awe”, but the word is now also a common colloquial expression. It was originally so used in the United States, where it had featured strikingly in the 1970 film Tora! Tora! Tora!, as used by Japan's Admiral Isoroku Yamamoto to describe the "awesome" industrial potential of the United States. Consequently, as the word popularly became an expression for anything superb, in its original meaning it has tended to be replaced by the related word, awe-inspiring. awe comes from Middle English aw, awe, agh, awȝe, borrowed from Old Norse agi, from Proto-Germanic agaz (“terror, dread”), from Proto-Indo-European h₂egʰ- (“to be upset, afraid”). Displaced native Middle English eye, eyȝe, ayȝe, eȝȝe, from Old English ege, æge (“fear, terror, dread”), from the same Proto-Germanic root.
Etymology from Wiktionary, CC BY-SA