You are correct! A one liner joke means a joke that is only told in "one line" meaning it doesn't need a response from another person and a final punch line from the joke teller. A funny (somewhat morbid) one liner joke: The early bird might get the worm, but the second mouse gets the cheese. I've never heard of an "out-line joke" so I can't help you there...

I have never heard of Out-line jokes. Where did you come across this term ? Technically, an OUTLINE is "a sketch depicting the outer edges of a person or object, without interior details or shading." So jokes that are shown as pictures with outlines speaking to each other may be called outline jokes. In that sense, they are different from one-liners because Outlines are pictorial whereas one liners are text based. Also, a one-line jokes are also called one-liners in short. However, one line is different (and means a single line) similarly, outlines are sketches whereas out-line jokes might be jokes based on those sketches. So they are different as well.