Something that’s random is lacking in order, plan, or purpose. It happens totally by chance, like the random picking of lottery numbers or unplanned random acts of kindness.
Sometime in the 1980s, teenage slang hijacked the adjective random and tried to turn it into a word meaning weird, odd or out of place. As in "Dude! That guy wearing purple spandex at the party was so random!" But don't fall for it. Something that’s truly random is totally governed by chance and has no specific pattern, like choosing a card at random from a magician’s deck.