to examine, study, or inquire into systematically; search or examine into the particulars of; examine in detail.

to search out and examine the particulars of in an attempt to learn the facts about something hidden, unique, or complex, esp. in an attempt to find a motive, cause, or culprit

The police are investigating the murder.

to make inquiry, examination, or investigation.

verb

ignore

verb

be all ears , bug , case * , check out , check over , check up , consider , delve , dig , examine , explore , eyeball , feel out , frisk , give the once over , go into , inquire , inquisite , inspect , interrogate , listen in , look into , look over , look-see , make inquiry , muckrake , nose around , poke , probe , prospect , pry , put to the test , question , read , reconnoiter , research , review , run down , scout , scrutinize , search , sift , spy , stake out , study , tap , wiretap , analyze , audit , check , dissect , sound , survey