from The American Heritage® Dictionary of the English Language, 4th Edition
- interj. Used as a toast to someone's health while drinking.
from the GNU version of the Collaborative International Dictionary of English
- interj. Lit., may it do (you) good; -- a salutation used in well wishing, esp. among Germans, as in drinking healths; -- also used in the contracted form prost.
from The Century Dictionary and Cyclopedia
- Good luck to you: a salutation used in drinking healths and otherwise among Germans and Scandinavians, especially among university students.
German, from Latin prōsit, may it benefit, third person sing. subjunctive of prōdesse, to benefit; see proud.(American Heritage® Dictionary of the English Language, Fourth Edition)