special grade; top grade; high class
Used for the highest rank or quality tier in formal grading systems, such as certifications, competitions, or product classifications. Often implies a level above ordinary grades.
He holds a special-grade certification.
This tea is handled as a top-grade product.
special grade article; superfine brand
top-grade sake; finest quality sake
Compound of 特 (special) and 級 (grade, class). The reading とっきゅう is a regular sound change from とく + きゅう.