Already entrenched in the teen-age vocabulary are superlatives like ''def'' (the best). Words like ''stupid'' (terrific) and ''wack'' (awful) are now established in both the urban and suburban teen-age lexicon irrespective of class or color.

Hip-hop music and fashion are also becoming international. ''Hip-hop, the words, the look, the attitude, it's going strong in Japan, France, Germany, Belgium and England,'' said Afrika Bambaataa, who recently returned to New York from Italy. ''It's spreading around, becoming a worldwide culture.''

Mr. Bambaataa is a rapper, a disk jockey and record producer, and many consider him to be one of the musical progenitors of hip-hop.

Rap's influence on music is growing; gospel is now being sung to the hip-hop beat. Instead of waning in energy as mass acceptance increases, rap has continued to be enlivened by innovations and infusions of new talent. $50 Million for Concerts According to industry estimates, in the last four years stores have sold $240 million worth of rap records and tapes and fans have spent $50 million to see rap groups in concert.

The hip-hop look is taken for granted among urban youths - and increasingly, among suburban teen-agers as well. Necessary to the uniform are untied Reebok, Adidas, Nike or Avia sneakers; baseball caps worn at a jaunty angle; shirts and jackets with large logos; unisex Spandex, denim or bold-patterned pants; gold chains and jewelry spelling out the wearer's name; rings that span several fingers and knuckles, and headphone radios. The ultimate status symbol is a Jeep with a roll bar for passengers to grasp while rap songs blast from a def sound system.

Some mainstream companies, like Adidas, have simply made formal relationships with performers who were already wearing their products. Adidas USA's A-15 warmup suit was for years the unofficial tuxedo of the hip-hop rapocracy. Run-D.M.C. -which in 1984 became the first rap group to earn a gold record - had a best-selling record called ''My Adidas'' before the group formally signed a $2 million contract with the manufacturer in 1987.