disclusion1
/dɪˈskluːʒn/rare after 17th cent
noun
Exclusion; an instance of this.
Origin
Mid 17th century; earliest use found in Thomas Blount (1618–1679), antiquary and lexicographer. From classical Latin disclūsiōn-, disclūsiō state of being separated off (2nd cent. a.d. in Apuleius) from disclūs-, past participial stem of disclūdere + -iō.
disclusion2
/dɪˈskluːʒn/noun
Dentistry. Failure of opposing teeth to make contact (when the jaws are closed); an instance of this.
Origin
1960s; earliest use found in American Journal Orthodontics. Apparently a remodelling of disocclusion, with loss of the second syllable perhaps by association with e.g. inclusion, exclusion, conclusion, etc. Compare earlier (in dentistry) retroclusion.