the mind > attention and judgement > enquiry > investigation, inspection > secret observation, spying > procedures used in spying > surveillance [verb (transitive)] > observe (2)
To look at, examine, or observe closely or carefully; to see or behold; in modern use spec., to investigate with a spyglass or telescope.
transitive. To watch, notice, look at; to follow or observe, esp. stealthily or with criminal intent. Also with off. Also occasionally intransitive…