Smart Definition
Etymology
Pronunciation
cuartillo
quart
cuarto
quarter
+
-illo
diminutive suffix
Cuartillo means quart and can be thought of as cuarto0 (quarter0) + -illo1 (diminutive1), suggesting a 'small quarter' or a unit slightly smaller than a quarter.
noun
  1. quart
    An old Spanish unit of measure for liquids, equivalent to about half a liter
    El tabernero sirvió un cuartillo de vino. // The innkeeper served a quart of wine.