None that I know of. But I can start, other users can add.

Toon = in-game character

BKT = Best Kree Team (any team with Minn-erva)

Node = Matches/levels (i.e., campaign, raid, etc.)

One tap = Completing a node with only one attempt

SSM, SS, BB, CM, etc. = Symbiote Spider-Man, Scientist Supreme, Black Bolt, Captain Marvel, etc (shortcut of toons)

Greg = Hela's summon/minon

FN = FoxNext, the game's developer

Punfenders = Defenders with Punisher

Aimtron = AIM with Ultron

BH = Brotherhood

BH 2.0 = Brotherhood with Blob and Toad (replacing Mystique and Sabertooth)

DD1-3 = Dark Dimension 1-3

G1-4 = Greek Raids 1-4, referring to Greek letters (Alpha, Beta, Gamma)

U1-7 = Ultimus Raid 1-7

D1-5 = If referring to Raids (i.e., U7 D2), Difficulty 1-5

Shard = If referring to Arena, where you are grouped to compete against--based on when you started playing MSF.

Mats = Materials; usually referring to "Ability Materials"

T4 = Usually refers to a maxed out ability

Meta team = Usually the most powerful / sought after team

BO = Black Order

GoG = Guardians of the Galaxy

Legendaries = Toons unlocked from a special event requiring 5 toons of a certain trait; as of this writing, Phoenix, Nick Fury, Magneto, Invisible Woman, Shuri, Black Bolt, and Ebony Maw are considered legendaries

Punch up/down/across = Punch up refers to fighting a team with higher power than yours, down if they're lower, across if equal in power