say it: DAY-doh
dado is a noun and verb meaning "panel forming the lower part of an interior wall when it is finished differently from the rest of the wall". It carries 5 recorded senses.
a rectangular groove cut into a board so that another piece can fit into it
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for dado come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.