| Acronym | Meaning |
| J | Joking |
| JAF | Just A Friend |
| JAFA | Just Another F***ing Aucklander |
| JAPAN | Just Always Pray At Night |
| JAS | Just A Second |
| JAT | Just A Thought |
| JATQ | Just Answer The Question |
| JB | Jail Bait Jonas Brothers |
| JBH | Just Being Honest |
| JBT | Jack-Booted Thug |
| JBU | Just Between Us |
| JBY | Just Be Yourself |
| JC | Jesus Christ Just Curious Just Chilling |
| JCB | J C Bamford (excavator manufacturer) |
| JD | Jack Daniel’s |
| JDI | Just Do It |
| JDLR | Just Doesn’t Look Right |
| JDM | Japanese Domestic Market |
| JFF | Just For Fun |
| JFK | John Fitzgerald Kennedy New York airport Just For Kicks |
| JFN | Just For Now |
| JFT | Just For Today |
| JFTR | Just For The Record |
| JFY | Just For You |
| JFYI | Just For Your Information |
| JG | Juicy Gossip |
| JGB | Just Got Back |
| JGH | Just Got Home |
| JGI | Just Google It |
| JGL | Just Get Lost |
| JHC | Jesus H Christ |
| JHP | Jacketed Hollow Point (bullet) |
| JIC | Just In Case |
| JICYDK | Just In Case You Didn’t Know |
| JJ | Just Joking |
| JK | Just Kidding |
| JKD | Jeet Kune Do (Martial Art) |
| JLMK | Just Let Me Know |
| JLS | Jack the Lad Swing (band) |
| JLT | Just like that |
| JLUK | Just Letting You Know |
| JLY | Jesus Loves You |
| JLYK | Just Letting You Know |
| JM | Just Messing |
| JMA | Just Messing Around |
| JMHO | Just My Humble Opinion |
| JML | Just My Luck |
| JMO | Just My Opinion |
| JMS | Just Making Sure |
| JMT | Just My Thoughts |
| JN | Just Now |
| JOOC | Just Out Of Curiosity |
| JP | Just Playin’ |
| JPA | Just Playing Around |
| JPEG | Joint Photographic Experts Group Image file format |
| JROTC | Junior Reserve Officer Training Corps |
| JRPG | Japanese Role Playing Game |
| JS | Just Saying |
| JSMN | Just Shoot Me Now |
| JSP | Java Server Pages |
| JSU | Just Shut Up |
| JSYK | Just So You Know |
| JTB | Just Too Bad |
| JTC | Join The Club |
| JTLYK | Just To Let You Know |
| JTOL | Just Thinking Out Loud |
| JTOY | Just Thinking Of You |
| JTTY | Just To Tell You |
| JTUSK | Just Thought You Should Know |
| JUAD | Jumping Up And Down |
| JV | Junior Varsity, amateur |
| JW | Just Wondering |
| JWAS | Just Wait And See |
| JWD | Job Well Done |
| JWG | Just a Wild Guess |
| JWTK | Just Wanted To Know |
| JWTLYK | Just Wanted To Let You Know |
| JWU | Just Woke Up |
| JWW | Just Was Wondering |