From WordNet (r) 3.0 (2006) [wn]:
investigate
v 1: investigate scientifically; "Let's investigate the syntax
of Chinese" [syn: investigate, look into]
2: conduct an inquiry or investigation of; "The district
attorney's office investigated reports of possible
irregularities"; "inquire into the disappearance of the rich
old lady" [syn: investigate, inquire, enquire]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Investigate \In*ves"ti*gate\, v. t. [imp. & p. p.
Investigated; p. pr. & vb. n. Investigating.] [L.
investigatus, p. p. of investigare to investigate; pref. in-
in + vestigare to track, trace. See Vestige.]
To follow up step by step by patient inquiry or observation;
to trace or track mentally; to search into; to inquire and
examine into with care and accuracy; to find out by careful
inquisition; as, to investigate the causes of natural
phenomena.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Investigate \In*ves"ti*gate\, v. i.
To pursue a course of investigation and study; to make
investigation.
[1913 Webster]