The best replacement for undergrad is grad.

The best alternatives to undergrad are rated as following:
★★★★★  grad
★★★★  graduate
★★★  grad school
★★★  grad student
★  postgrad
★  graduate school
★  post grad
  graduate degree
  grad chapter
  law school
  under grad
  graduate student

Your alternative for undergrad is not listed? Suggest!
Speaking about undergrad, one probably shouldn't forget about mba.

Other search terms related to undergrad and their ratings are:
★★★★★ mba
★ grad
You have in mind a companion for undergrad and it is not yet here? Propose!



Google Trends

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undergrad
grad
graduate