1) Decimeter 2) French word used in English 3) Metric linear unit 4) Unit of length 1) Decimeter 
The decimetre (International spelling as used by the International Bureau of Weights and Measures; SI symbol dm) or decimeter (American spelling) is a unit of length in the metric system, equal to one tenth of a metre, the SI base unit of length (or ten centimetres). Equivalently, there are 10 decimetres in a metre. It is equivalent to 3.93700787 ...
• (n.) A measure of length in the metric system; one tenth of a meter, equal to 3.937 inches.
<unit> One-tenth of a metre. ... Equivalent to 3.973 inches, 10 cm, or 0.1 m. ... (09 Oct 1997) ... 
decimetre (British)
Abbreviated as dm, unit length equal to 10-1m. See also: Decimal Prefixes, Metre.