Definition of "keypoint"

keypoint

noun
plural keypoints
1. Part of a valley where the lower and flatter portion of the primary valley floor suddenly becomes steeper, used in computing a keyline for the efficient planning of water usage.
2. An important point in an image, used in computer vision systems when detecting objects etc.
  Quotations
  We use a deep convolutional neural network within an expectation maximization framework to take advantage of weakly labeled data like image level annotations or keypoint annotations.
  2016, Abhilash Srikantha, Juergen Gall, “Weakly Supervised Learning of Affordances”, in arXiv‎