Same as postal card (which see, under postal).(noun)
The Century Dictionary (Public Domain)
Use "post-card" in a sentence
"Every ounce of its dust passed through his hands; every post-card and letter of credit."
"Given the open nature of the communication, and the fact that transcripts have to be retained for billing purposes (unlike for example e-mail), would you conclude that this is the electronic equivalent of a post-card and that no expectation of privacy exists entirely?"
"Your photo is proudly displayed in Kristi's post-card rack in her kitchen, so I saw you each morning as I poured my coffee."