What is the meaning of overlap?

noun

• A representation of common ground between theories or phenomena.
  • usage: "there was no overlap between their proposals"
  • synonyms: convergence, intersection
• The property of partial coincidence in time.
• A flap that lies over another part.
  • usage: "the lap of the shingles should be at least ten inches"
  • synonyms: lap

verb

• Coincide partially or wholly.
  • usage: "Our vacations overlap"
• Extend over and cover a part of.
  • usage: "The roofs of the houses overlap in this crowded city"