Synonyms and related words :
be vigilant, be watchful, bug, case, course, cover, do, eye, eyeball, follow, gaze at, go over, have a looksee, hold in view, keep in sight, keep in view, keep under observation, look after, look at, look on, look upon, make a reconnaissance, measure, observe, overpass, pass over, pass through, patrol, peep, perambulate, peregrinate, pererrate, play the spy, ply, probe, put under surveillance, range, range over, regard, scour, scour the country, scout, scout out, spy, spy out, spy upon, stake out, sweep, track, transit, travel over, travel through, traverse, view, voyage, watch