The Collaborative International Dictionary
Tenthmetre
Tenthmeter \Tenth"me`ter\, Tenthmetre \Tenth"me`tre\, n. (Physics) A unit for the measurement of many small lengths, such that 10^ 10 of these units make one meter; the ten millionth part of a millimeter.
Wiktionary
tenthmetre
n. (alternative form of tenthmeter English)