A perfect rhyme for the word "breakfast" is "wreckfest" (2 syllables) and the phrase "bed-and-breakfast" (4 syllables)1.

There are also several near or slant rhymes that could work depending on context, such as:

• words ending in "-fast" like "bedfast," "handfast," "makefast"
• words with similar sound endings like "trust," "just," "dust," "thrust," "robust"
• some multisyllabic words that share the "-fast" sound

However, the only perfect single-word rhyme specifically listed is "wreckfest"13.

So for a precise rhyme with "breakfast," "wreckfest" is the best match, while "bed-and-breakfast" is a matched phrase rhyme. Otherwise, slant rhymes and near rhymes like "trust," "dust," or "just" are options for creative uses.