This meaning of degenerate is discussed in more detail at: Degeneracy (mathematics) on Wikipedia.
There is another related meaning of degenerate that you may encounter, which is a special case of the previous definition -- a degenerate matrix is one which is not invertible (Invertible matrix, Wikipedia). This can come up when solving a system of linear equations (KCL or KVL) if you mistakenly use the same equation twice, for example.