a drug whose use may make it more likely that someone uses other, more dangerous, drugs

Early intervention could prevent adolescents from "graduating" from so-called gateway drugs such as alcohol and marijuana to harder drugs such as meth. 早期干预可以防止青少年从酒精和大麻等所谓的入门毒品 "发展"到冰毒等更具危险性的毒品。

something that makes you more likely to try other things that are similar but more unusual or difficult

Stephen King was my gateway drug to serious literature. 斯蒂芬 · 金的作品带领我进入了严肃文学的殿堂。