n. A substance that does not transmit heat (thermal insulator), sound (acoustic insulator) or electricity (electrical insulator).
n. A non-conductive structure, coating or device that does not transmit sound, heat or electricity (see image)
the GNU version of the Collaborative International Dictionary of English
n. One who, or that which, insulates.
n. A substance or object that insulates; a nonconductor.
The Century Dictionary and Cyclopedia
n. One who or that which insulates; specifically, a substance or body that interrupts the communication of electricity or heat to surrounding objects; a non-conductor; anything through which an electric current will not pass.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a material such as glass or porcelain with negligible electrical or thermal conductivity
Word Usage
"And the crowning glory, the "green" sedum roof – actually more of a russet colour – on the Newton building, which acts as a natural insulator, helps prevents flash flooding and provides a haven for birds, bees and butterflies."