It's an approach in economics that usually rejects Marx's revolutionary politics but agrees with his critiques of capitalism. People like Richard Wolff identity as Marxian.
Yeah it's not required but the only self identified "Marxians" I've come across were raging liberals while I have met "Marxist" academics that were not liberal.
Someone needs make this a bit, with like, lore from 4th level down trotsky group splits.
"No, like, Marxian means you're aligned with the 4.89th solid international, while Marxist means you joined the 4.91th liquids because you disagree with the previous's stance on the peasant question (hypothetical moon-based peasants to be precise)."