unbreakable
1. [ adjective ] impossible to break especially under ordinary usage
Examples:

"unbreakable plastic dinnerwear"

Related terms: breakable shatterproof infrangible breakableness
2. [ adjective ] impossible to not honor
Examples:

"an unbreakable promise"

Related terms: inviolable
Similar spelling:   unbearable
  unprovable
  unforeseeable
  unprintable
  unbridgeable
  unbearably
  unprofitable
  unprocurable