Frequent flyers and points nerds pride themselves on myriad terms, acronyms, and shortenings. Typically, this is for convenience and shorthand rather than a desire for illegibility. In that spirit, here are some terms that I commonly use and see used by others.

Flights

Routings

TCON/Transcon: Trans-continential flights. Some routes may have a higher level of service on US airlines, such as SEA/SFO/LAX-BOS/JFK/IAD

TPAC: Flights that cross the Pacific Ocean

TATL: Flights that cross the Atlantic Ocean

Fare Classes

Y: Economy Class

PY: Premium Economy. These are seats with upgraded meals, extra legroom, footrests, mainly found on long-haul flights. Not to be confused with "extra legroom"/"premium" seats found on domestic flights with US carriers)

J: Business Class

F: First Class. Can also refer to domestic "First Class" on US3

Mileage Programs

SQM/MQM/EQM: Status/Medallion/Elite Qualifying Miles, miles flown that are tracked towards elite status. Usually used in contrast with RDMs.

RDM: Redeemable Miles, i.e. the currency used by airlines to redeem flight awards. Usually used in contrast with SQM/MQM/EQM, which are miles required to qualify for elite status

SQD/MQD/EQD: Status/Medallion/Elite Qualifying Dollars, amount of base fare that must be spent in addition to *QM/*QS needed to qualify for elite status

SQS/MQS/EQS: Status/Medallion/Elite Qualifying Segments, amount of segments flown to qualify for status.

Airlines

LCC: Low Cost Carrier, such as RyanAir, Southwest

ULCC: Ultra Low Cost Carrier, such as Spirit, AirAsia, Porter

US3: The three legacy US carriers: American, Delta and United

ME3: The three five-star Middle Eastern based airlines: Qatar (QR) with a hub in Doha, Emirates (EK), with a hub in Dubai, and Etihad (EY), with a hub in Abu Dhabi

OW - Oneworld

AA: American Airlines

AS: Alaska Airlines

JL/JAL: Japan Airlines

BA: British Airways

QR: Qatar Airways

CX: Cathay Pacific

ST - SkyTeam

DL: Delta Air Lines

AF: Air France

KL: KLM Royal Dutch Airlines

*A - Star Alliance

UA: United Airlines

SQ: Singapore Airlines

NH: All Nippon Airways (ANA)

LH: Lufthansa

AC: Air Canada

LX: SWISS

ME3

QR: Qatar Airways (oneworld)

EK: Emirates (partnered with Air Canada)

EY: Etihad

Hotels

SNA/SUA: Suite Night Awards/Suite Upgrade Awards - Instrument/certificate used to waitlist an upgrade to a suite

FNA/FNC: Free Night Awards/Free Night Certificates - Instrument/certificate used to book a free night stay, subject to normal award booking restrictions. Usually capped at a hotel category or points threshold.

Transferrable Points Programs

UR: Chase Ultimate Rewards

MR: American Express Membership Rewards

TYP: Citi ThankYou Rewards