A verse using internal rhyme in which the middle and end of each line rhyme.
More specifically, in the leonine verse of medieval Latin, hexameters (or alternate hexameters and pentameters) would have the word before the caesura and the final word in each line rhyme with each other, such as the ecclesiastical Stabat mater.
That made no sense to me. So, here’s an example.
C. H. Holman provides the following Latin example with slightly less grandeur than the Stabat mater:
Ex rex Edvardus, debacchans ut Leopardus
Here, the bold letters illustrate the leonine rhyme.
These fancies were common in the 12th century, and were so called from Leoninus, a canon of the Church of St. Victor, in Paris, the inventor.
In English verse, any metre which rhymes middle and end is called a Leonine verse.
An English example appears in Tennyson’s The Revenge:
And the stately Spanish men to their flagship bore him then,
Where they laid him by the mast, old Sir Richard caught at last,
And they praised him to his face with their courtly foreign grace.