An opaque disc of gas and dust orbiting a young star, thought to be an embryonic planetary system; a protoplanetary disc.
1990s; earliest use found in United Press International Newswire. From pro- + -pl- + -y + d-.
英汉双解词典包含464360条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。