An Etymological Dictionary of Astronomy and Astrophysics

1. (v.tr.) To lap over something else; extend over and cover a part of.
   

2. (v.intr.) To lap over.
   

3a) Math.: Of sets, to have one or more elements in common.

3b) Chemistry: The interaction of orbitals on different atoms in the same region of space.

3c) Meteo.: The area common to two successive satellite images or scan swaths along the same or adjacent flight or orbital strips. The amount of overlap is expressed as a percentage of image area or scanned area.

Etymology (EN): → over- + lap, verb from noun lap, from O.E. læppa “skirt or flap of a garment,” from P.Gmc. *lapp- (cf. M.Du. lappe, O.H.G. lappa, Ger. Lappen “rag, shred”).

Etymology (PE): 1) Barham nehâdan, from barham “one over the other” (for etymology of bar-, → on-; for etymology of ham-, → com-) + nehâdan “to place, put; to set” (Mid.Pers. nihâtan;
Av. ni- “down; below; into,” → ni-,

• dā- “to put; to establish; to give,” dadāiti “he gives;” cf. Skt. dadāti “he gives;” Gk. didomi “I give;” L. do “I give;” PIE base *do- “to give”).
  

2. Barham nešastan, from barham, as above, + nešastan “to sit;” Mid.Pers. nišastan “to sit;” O.Pers. nišādayam [1 sg.impf.caus.act.] “to sit down, to establish,” hadiš- “abode;” Av. nišasiiā [1 sg.subj.acr.] “I shall sit down,” from nihad- “to sit down,” from ni-, as above,

• had- “to sit;” PIE base *sed- “to sit;” cf. Skt. sad- “to sit,” sidati “sits;” Gk. hezomai “to sit,” hedra “seat, chair;” L. sedere “to sit;” O.Ir. suide “seat, sitting;” Welsh sedd “seat;” Lith. sedmi “to sit;” Rus. sad “garden;” Goth. sitan, Ger. sitzen; E. sit.
  

3. → overlapping.