[′hü·drē ¦fixt ¦bed ‚kad·əl¦id·ik ′krak·iŋ] (chemical engineering) A cyclic, regenerable process for cracking of petroleum distillates to produce high-octane gasoline from higher-boiling petroleum fractions; synthetic or natural bead catalysts of activated hydrosilicate of alumina may be used. Also known as Houdry process.