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][1]
>
>**Holidays**: Application defect whereby small areas are left uncoated. Synonyms: *Misses*, *Skips*, *Voids*, *Discontinuities*, *Vacations*.

and from *[Coating Defects-Common Coating Failures and Causes][2]*

> - Coating Defects: ***Runs***, ***Sags***, ***Curtains***, ***Wrinkles*** 
[![enter image description here][3]][3]  
>*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][4]**, used in the painting industry, is also appropriate.

>**Curtains**   
>Large sagging or runs of paint due to improper application.


  [1]: http://www.thepaintersexpress.com/paint_coatings_glossary.html
  [2]: http://www.capital-painting.com/coating-defects/
  [3]: https://i.sstatic.net/mzpy9.jpg
  [4]: http://www.sharpe1.com/sharpe/sharpe.nsf/Page/Paint+Terminology