means the practice of sending fraudulent messages that impersonate trusted sources to trick you into revealing passwords, card numbers, or other sensitive information.

from A deliberate misspelling of "fishing" — you bait a hook and wait for someone to bite. It emerged in 1990s hacker culture, where swapping "f" for "ph" was a stylistic tradition borrowed from "phreaking" (the older art of hacking phone systems). So phishing is fishing for victims, dressed up in hacker spelling.