[′hēt di‚stȯr·shən ‚pȯint] (engineering) The temperature at which a standard test bar (American Society for Testing and Materials test) deflects 0.010 inch (0.254 millimeter) under a load of either 66 or 264 pounds per square inch (4.55 × 105 or 18.20 × 105 pascals), as specified.