Sight rhymes are rhymes that look like rhymes. They have the same ending letters that you would find in rhyming words but, alas, the combinations of letters are pronounced differently. Such is the nature of the English language.
"Sighted Rhymes, Sank Same,"
Word Ways: Vol. 36
, Article 7.
Available at: http://digitalcommons.butler.edu/wordways/vol36/iss1/7