Movement or position across something; transverse; interaction; cross-shaped; marked with a cross.
Cross has many meanings; the prefix reflects that, to the extent it is not always possible to tease out clearly defined and distinct senses for it. Examples where it has the idea of movement across something include crossfire, cross-channel, cross-border, crossover, cross-fade, cross-country. Other words suggest two thing lying across each other at an angle: cross-legged, cross-eyed, cross-grained, cross-ply, crossbill. Some denote an interaction between two things: cross-pollinate, cross-breed, cross-fertilize, cross-examine, cross-index, cross-check, cross-refer, cross-subsidize. The idea of something transverse appears in crossbar and crosspiece. An implication that the form of a cross is present is found in crossbones (as in skull and crossbones), cross-bun, crossbow, crossroads, and crossword.