unbound

adjective5

1. •
   Not bound.
2. •
   Not tied up.

   • The hostages' hands were left unbound.
3. •
   Without a binding.

   • an unbound book
4. •
   Not obligated.

   • The terms of the contract inadvertently left certain unbound aspects to subjective interpretation.
5. •
   Lying beyond the proton or neutron drip line; having a negative particle separation energy; capable of decaying by the spontaneous exothermic emission of one or more nucleons.

   • Helium-2 is unbound, as it is energetically favorable for it to split into two separate protons.