mentalist noun 2adjective 1forms 3 noun2 •A practitioner of mentalism. •(UK, slang) An insane person.Jed Maxwell: See you next week then. We'll have that pint. Alan Partridge: Yep. Jed Maxwell: ...go and see my brother. Alan Partridge: No way, you big spastic! You're a mentalist! — 1997 adjective1 •Of or relating to mentalism formsmentalists · more mentalist · most mentalist