We found 3 dictionaries that define the word bread and butter letters:

General (2 matching dictionaries)

1. bread-and-butter letters, bread-and-butter letters: Collins English Dictionary
2. bread-and-butter letters: Wiktionary

Miscellaneous (1 matching dictionary)

3. bread-and-butter letters: Idioms

▸ Words similar to bread and butter letters ▸ Usage examples for bread and butter letters ▸ Idioms related to bread and butter letters ▸ Wikipedia articles (New!) ▸ Words that often appear near bread and butter letters ▸ Rhymes of bread and butter letters ▸ Invented words related to bread and butter letters