Merriam-Webster's Collegiate Dictionary
pre·oc·cu·py
\\-ˌpī\\ transitive verb ETYMOLOGY Latin praeoccupare, literally, to seize in advance, from prae- + occupare to seize, occupy
DATE 1567
1. to engage or engross the interest or attention of beforehand or preferentially2. to take possession of or fill beforehand or before another Oxford Advanced Learner's Dictionary-牛津双解-OALD7
preoccupy
pre·occupy / pri5Ckjupai; NAmE -5B:k- / verb (pre·occu·pies, pre·occu·py·ing, pre·occu·pied, pre·occu·pied)
[VN] if sth is preoccupying you, you think or worry about it very often or all the time
使日夜思考；使忧心忡忡
Webster's Third New International Dictionary, Unabridged
pre·occupy
\(ˈ) ̷ ̷+\
transitive verbEtymology: pre- + occupy1. : to engage, occupy, or engross the interest or attention of beforehand or preferentially
: preengage
,
prepossess
2. : to occupy or take possession of before another
< preoccupy a country not before held > 3. : to fill beforehand : occupy in advance of