undergraduate
牛津词典
1、本科生
a university or college student who is studying for their first degree
柯林斯词典
1、N-COUNT 在校本科生;大学生
An undergraduate is a student at a university or college who is studying for his or her first degree.
朗文词典
1、[C] （在读的）大学（本科）生
a student at college or university, who is working for their first degree
graduate
牛津词典
noun
1、~ (in sth) 大学毕业生；学士学位获得者
a person who has a university degree
2、(NAmE) 毕业生
a person who has completed their school studies
verb
1、[V] ~ (in sth) | ~ (from…) 获得学位（尤指学士）；大学毕业
to get a degree, especially your first degree, from a university or college
2、[V] ~ (from…) (NAmE) 毕业（尤指中学）
to complete a course in education, especially at high school
3、[VN] ~ sb (from sth) (NAmE) 授予（某人）学位（或毕业文凭等）
to give a degree, diploma , etc. to sb
柯林斯词典
1、N-COUNT （英国的）大学毕业生，学士学位获得者
In Britain, a graduate is a person who has successfully completed a degree at a university or college and has received a certificate that shows this.
2、N-COUNT （美国的）高中（或学院、大学）毕业生
In the United States, a graduate is a student who has successfully completed a course at a high school, college, or university.
3、VERB （英国）大学毕业
In Britain, when a student graduates from university, they have successfully completed a degree course.
4、V-ERG （美国）中学（或大学）毕业，授予…学位（或毕业文凭）
In the United States, when a student graduates, they complete their studies successfully and leave their school or university. You can also say that a school or university graduates a student or students.
朗文词典
n [C]
1、（尤指完成学士学位课程的）大学毕业生
someone who has completed a university degree, especially a first degree
2、【美】（大学、中学等的）毕业生
AmE someone who has completed a course at a college, school etc
postgraduate
牛津词典
1、(especially BrE) 研究生
a person who already holds a first degree and who is doing advanced study or research; a graduate student
柯林斯词典
1、N-COUNT 研究生
A post-graduate or a postgraduate student is a student with a first degree from a university who is studying or doing research at a more advanced level.
美国英语用 graduate student
朗文词典
1、[C]【尤英】（硕士或博士）研究生 = graduate student AmE【美】
especially BrE someone who is studying at a university to get a master's degree or a PHD
