obsess
Concise Oxford English Dictionary © 2008 Oxford University Press:
obsess/əbˈses/
▶verb preoccupy continually or to a troubling extent.
■ be constantly worrying about something.
– derivatives
obsessive adjective & noun,
obsessively adverb,
obsessiveness noun.
obsessive adjective & noun,
obsessively adverb,
obsessiveness noun.
– origin ME: from L. obsess-, obsidere ‘besiege’.
'obsess' also found in these Oxford entries:
