Definitions of overlap:

• noun:   the property of partial coincidence in time
• noun:   a representation of common ground between theories or phenomena

  Example: "There was no overlap between their proposals"

• noun:   a flap that lies over another part
• verb:   coincide partially or wholly

  Example: "Our vacations overlap"

• verb:   extend over and cover a part of

  Example: "The roofs of the houses overlap in this crowded city"