flash

1. n. [Unix] A little program intended to quickly turn a user's
terminal display into garbage by sending VT-100 escape characters
over the network, forcing a user to logout.

In 1990s, most Unix systems were owned by institutions and timeshared
among users. A talk daemon (talkd, ntalkd, walld) on these systems allowed
users to exchange short messages on terminals, locally or over the network
from another system. "flash" exploited it to send escape characters, and
was a common instrument for pranks and in-fights on MUD and IRC, and a major
nuisance at that time.

For examples in source code, see https://seclists.org/bugtraq/1994/Jul/16 and
http://phrack.org/issues/47/4.html (grep "flash").

2. v. [Unix] The act of sending unsolicited escape sequences to disrupt
a user's terminal. When the terminal is incapacitated, that's to say a
user "gets flashed".

It was commonly exploited via talkd using the "flash" program, but
originally used in finger (via ~/.plan), and achievable everywhere where
escape sequences are accepted, such as mail clients (via emails) and
ZModem.

3. n. Adobe Flash, a deprecated multimedia software by Adobe. Despite
millions of web games based on it, and widespread use for animation
and videos in web pages, it has performance issues, especially for
video playbacks, and infamous in the hacker community for numerous
security vulnerbilities and its use in online advertising popups.
It faced a backlash when Steve Jobs refused to allow it in Apple's
iOS products, and gradually fallen into disuse in favor of HTML 5 and
JavaScript.

4. n. Flash memory, a solid-state non-volatile data storage medium.
It's used universally in USB drives, mobile and embedded devices.
It has became an alternative over the classical mechanical data
storage medium since 2010s due to its advantage of being fully
electronic without moving parts and fallen price.