The following is an item in the first core 100 deck in absolute beginner. As you can see, the Korean word 정각 does not appear in the example sentence. The word 시에 is in the sentence and does mean "o'clock". I suspect that 정각 does not mean "o'clock".
Could you please clarify:
정각 (noun) jeonggak o'clock 아홉 시에 역에서 만나요. Ahop sie yeogeseo mannayo. Let's meet at the station at 9 o'clock.
Thank you for posting. Actually, 정각 means 'exactly ~:00', so if it is exactly 1pm, you would write 오후 1시 정각. So technically the example should have been written as '세 시 정각에'. However, people will sometimes omit it as it makes it sound a bit 'rigid', and simply say ~시에 만나요 (세 시에 만나요). Hope this was of help!