Claudio, 
When I think of "alligator" cracking, is is a deterioration in what ever finish
was used on the piece, it is cracked and crazed, almost like cross checking
which kind of resembles rough lizard skin...hence the name "alligator" or
crocodile.

Here is a link with some good examples:  http://www.fullchisel.com/albu
rnam22.htm">http://www.fullchisel.com/alburnam22.htm

Hope this helps

Brent A Kinsey