noun

• (uncountable) Similarity or resemblance to something else.
  "So am I tossed on the ebbing tide of life—now in sunshine, now in shade—seemingly free, yet, in reality, fettered by the strong, though slight chain of circumstance. For a small sum, any passenger may enter that boat and direct its course; and here again is similitude. I am at the beck of others."
• (countable) A way in which two people or things share similitude.
  "Aemulation was similitude within distance: the sky resembled a face because it had “eyes” — the sun and moon."
• (countable) Someone or something that closely resembles another; a duplicate or twin.
  "If I was certain of anything in the world, I was certain that I had seen my brother in the study — nay, more, had touched him, — and equally certain that I had seen his double — his exact similitude, in the garden."
• (countable, geometry) A similarity: a transformation of Euclidean space that preserves angles and the ratios of distances.