What does across mean?
The definition of across
A*cross” (#; 115), prep.
Etym: [Pref. a- + cross: cf. F. en croix. See Cross, n.]

From side to side; athwart; crosswise, or in a direction opposed to the length; quite over; as, a bridge laid across a river. Dryden. To come across, to come upon or meet incidentally. Freeman.

— To go across the country, to go by a direct course across a region without following the roads.

A*cross”, adv.
1 From side to side; crosswise; as, with arms folded across. Shak.
2 Obliquely; athwart; amiss; awry. [Obs.] The squint-eyed Pharisees look across at all the actions of Christ. Bp. Hall.