unbound

• IPA^(key): /ʌnˈbaʊnd/

• Audio (Southern England)

  (file)

• Rhymes: -aʊnd

unbound

1. simple past and past participle of unbind

• unbounded

unbound (not comparable)

1. Not bound; not tied up.

   The hostages' hands were left unbound.

2. Without a binding.

   an unbound book

   • 1880, William Blades, The Enemies of Books, page 40:

     Beneath an old ebony table were two long carved oak chests. I lifted the lid of one, and at the top was a once-white surplice covered with dust, and beneath was a mass of tracts — Commonwealth Quartos, unbound — a prey to worms and decay.

3. (nuclear physics, of an atomic nucleus) 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.