What rhymes with penultimate?

That depends on how many of the final syllables have to match for a Word or phrase to be considered rhyming. As a general rule of thumb, any string of syllables which is roughly the same length as a given string and ends in the same consonant cluster-vowel cluster or vowel cluster-consonant cluster can be considered rhyming, so, for the Word 'penultimate' (usually pronounced either [pɪ'nɑl'tɪmɪt] or [pɪ'nəl'tɪmɪt] or [pɪ'nəl'tɪmət]) , any Word or phrase consisting of at least 3 syllables and ending in, depending on the pronunciation of 'penultimate', either [ət] or [ɪt] would constitute a rhyme. Some examples would include "Should I get..." (some dialects mach [ɪt], others [ət]), "Baseball mitt" (most, if not all, dialects match [ɪt]), "I haven't met" (some match [ət], others [ɪt]), and "to place a bet" (most dialects match [ət]).