Polymeric or oligomericsiloxanes, usually considered unbranched, of general formula $\ce{[–OSiR2–]_{n}}$ ($\ce{R} \neq \ce{H}$).
Source: PAC, 1995, 67, 1307. (Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)) on page 1366 [Terms] [Paper]