Yesterday, a newcomer named Pen posted the following answer:
We grew up calling them 'holidays'.
The answer has since been deleted. It seemed an odd answer, but it didn't sound offensive or gratuitous to me. So, I looked online and found the following definitions:
Painting and Coatings Terms and Definitions
Holidays: Application defect whereby small areas are left uncoated. Synonyms: Misses, Skips, Voids, Discontinuities, Vacations.
and from Coating Defects-Common Coating Failures and Causes
Coating Defects: Runs, Sags, Curtains, Wrinkles
Runs, sags, curtains, or wrinkles may be caused or worsened by: applying the coating too thickly, using too much thinner or using the wrong thinner, surface too hot to apply the coating, applying a coating at the end of its pot life, wrong thixotrope used in manufacturing , improper spray technique.
Discontinuities: Skips, Holidays, and Missed Areas
These defects are exposed areas of the substrate or previous coating, caused by poor application technique, lack of stripe coating, and/or lack of or poor inspection. Quick recognition and repair means the repair is easier and it will blend in better.
If the drips or ‘sags’ are large then the term curtains, used in the painting industry, is also appropriate.
Large sagging or runs of paint due to improper application.