midbrain midaxillary • midday · · · Info · Definitions · Synonyms · Characters · · midbrain · · Text Latin · · Script 8 · · Length Definitions · · · (noun) the middle portion of the brain. Synonyms: mesencephalon. · · Noun Definition 1 Synonyms · · · mesencephalon · · Synonym 1 Characters · · a latin small letter a U+0061 b latin small letter b U+0062 d latin small letter d U+0064 i latin small letter i U+0069 m latin small letter m U+006D n latin small letter n U+006E r latin small letter r U+0072