I'll attempt to expand upon daniel's answer above.
Boudin describes a sausage that is generally created from a blend of beef, rice, and/or pork ("What is Boudin", Cajun French Blog 2009). Sometimes other types of proteins are added to create variations: Gator, Shrimp, crawfish, etc.
Boudin is widely known to be used in Cajun cooking. Other various types of Boudin exists. As wikipedia defines various different types of boudin:
Boudin blanc: A white sausage made of pork without the blood. Pork
liver and heart meat are typically included. In Cajun versions, the
sausage is made from a pork rice dressing [...] In
French/Belgian cuisine, the sausage is sauteed or grilled. The
Louisiana version is normally simmered or braised, although coating
with oil and slow grilling for tailgating is becoming a popular option
in New Orleans and Baton Rouge.
Boudin noir: A dark-hued blood sausage, containing pork, pig blood, and other ingredients. Variants of the boudin noir occur in French, Belgian, Cajun and Catalan
Shrimp Boudin: Similar to crawfish boudin, it is made by adding the shrimp to rice [...]
 Boudin rouge: In Louisiana cuisine, a sausage
similar to boudin blanc, but with pork blood added to it. This
originated from the French boudin noir.
Brown Rice Boudin: Taste is very similar to traditional pork boudin, except this boudin > is made with a brown-rice substitute for those looking to cut down on white rice intake.