PST
PST has 2 meanings
Please send tell
In online gaming, PST is synonymous with "DM me." You're most likely to encounter this acronym while playing an MMORPG, when another player wants you to send them a private message.
Origin of PST
In old MUDs and MMORPGs, players often used the command "tell" to send each other private messages. Thus, if a player wanted to converse via private message, they'd ask another player to Please Send Tell, or PST.
Some modern MMORPGs retain this usage of /tell. For example, in FFXIV, players can use the /tell command to send a DM, and in WoW, players can use /t (short for /tell). Thus, MMORPG players still frequently use the PST acronym to request DMs.
Example
LF1M for raid group. PST if interested
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An acronym that refers to the PT when DST ends; often appears next to television program listings; 1 hour behind MST, 2 hours behind CST, and 3 hours behind EST; consists of the west coast of parts of Canada, Mexico, and the U.S.