https://www.merriam-webster.com/dictionary/United%20States%20standard%20thread
UNITED STATES STANDARD THREAD Definition & Meaning - Merriam-Webster
The meaning of UNITED STATES STANDARD THREAD is an American screw thread that has a thread angle of 60 degrees and varies from 31/2 to 64 threads per inch.
united states standard threaddefinitionmeaningmerriamwebster