From Longman Dictionary of Contemporary Englishmightymight‧y1 /ˈmaɪti/ ●●○ adjective (comparative mightier, superlative mightiest) literaryIMPRESSvery strong and powerful, or very big and impressive
the mighty Mississippi river
a mighty army →high and mightyExamples from the Corpusmighty• Above all we give thanks to thee for that thou artmighty.• The cannonexplodes with a mightycrack.• Denver ran a mightyinterference and on the third day flat-out asked Paul D how long he was going to hang around.• Their only win was a 1-point thriller, at home, over those mighty Minnesota Timberwolves.• But the vehicle itself is the mightytransnationalcorporation.• Dedicated to All Saints, the church is tucked away behind mightytrees on a high bank of the river.• mightywarriors• Ah, the roar of nations, they roar like the roaring of mighty waters!mightymighty2 adverbAmerican English informalVERY very
You seem mighty sure of your facts.
They got out of there mighty fast, I can tell you.Examples from the Corpusmighty• That's a mighty big fish.• Because the inside of the nose is mightyirritated, you involuntarily sneeze to clear it.• You seem mightysure of it.