1. a random statement used in a group to cause gaiety
2. a vague sexual reference
Generally used after a lull in conversation, preferably in a southern accent.
For example: A group of friends are frying up some snails for dinner while shooting everclear, and after a LULL in conversation the jokester in the group says butter my bread (emphasis on the southern accent, especially on the bread).
The group is left stunned and confused at the unknown phrase, and laughter abounds.