The Collaborative International Dictionary
Subduple
Subduple \Sub"du*ple\, a. (Math.) Indicating one part of two; in the ratio of one to two.
Subduple ratio, the ratio of 1 to 2: thus, 3:6 is a subduple ratio, as 6:3 is a duple ratio.
Wiktionary
subduple
a. (context mathematics English) Indicating one part of two; in the ratio of one to two.