1. Everyday; commonplace: “There’s nothing quite like a real . . . train conductor to add color to a quotidian commute”Anita Diamant.
2. Recurring daily. Used especially of attacks of malaria.
[Middle English cotidien, from Old French, from Latin qutdinus, from qutdi, each day : quot, how many, as many as; see kwo- in Indo-European roots + di, ablative of dis, day; see dyeu- in Indo-European roots.]