1 a place where things (esp. roads) cross.
2 a place at which one may cross a street etc. (pedestrian crossing).
3 a journey across water (had a smooth crossing).
4 the intersection of a church nave and transepts.
5 Biol. mating.
Phrases and idioms:
crossing over Biol. an exchange of genes between homologous chromosomes (cf. RECOMBINATION).
Useful english dictionary. 2012.