Thor's hammer

Short definition from Wiktionary

Noun

1. 1
   Mjöllnir (Mjollnir), the distinctively T-shaped war-hammer of the Norse thunder god Thor, or a representation thereof, now used as a symbol by various pagan religious groups.
2. 2
   An orbital drop hypervelocity kinetic energy weapon (KEW). A theoretical weapon, originating from a U.S. government study, Project Thor, from the 1950s.