The intentional clearance, created between mating threads, is called the "allowance:"

https://www.fastenal.com/content/feds/pdf/Article%20-%20Screw%20Threads%20Design.pdf

(I recall that the galvanized bolts at Home Depot have "looser" threads.)

http://rick.sparber.org/nbo.pdf
http://rick.sparber.org/spt.pdf

- Brian