Cross-processing
means developing film in non-compatible chemistry.  Transparency film (except Kodachrome) uses E6 chemistry and print film uses C41 chemistry.  With cross-processing you reverse the above film/chemistry combinations.

Tech tips from Christopher Aradanas:

Basically, CP increases contrast. So if you don't want your shadow details to get lost, you should shoot in non-contrasty, flat, even lighting and overexpose by one half to one stop. On the other hand one is encouraged to experiment. For more

resource 1

resource 2 (useful info but it is pop-up window central)