cofferdam coffer • cofferer · · · Info · Definitions · Synonyms · Characters · · cofferdam · · Text Latin · · Script 9 · · Length Definitions · · · (noun) large watertight chamber used for construction under water. Synonyms: caisson, pneumatic caisson. · · Noun Definition 1 Synonyms · · · caisson · · Synonym 1 pneumatic caisson · · Synonym 2 Characters · · a latin small letter a U+0061 c latin small letter c U+0063 d latin small letter d U+0064 e latin small letter e U+0065 f latin small letter f U+0066 m latin small letter m U+006D o latin small letter o U+006F r latin small letter r U+0072