I agree with Mike, somewhat. I consider a deathfic to be when a main or beloved co-starring character (See Mike's list of characters) dies and said death is a main component of the story. While I'd add Cat Grant to his list, many others would not. Oh, wait, Bill Henderson should be added too. I might add other beloved characters known to the readers but not necessarily canon. If Batman, Wonder Woman, other main Justice League members, and previous and loved spouses to Lois and Clark, or any children of Lois and Clark were to die, it could also make the story a deathfic. This only applies, if said character were introduced to the reader within the story and died within the scope. If Batman were to die and neither Lois or Clark had known him nor were affected by his death, then I wouldn't consider it a deathfic. (Although, WE all know that Clark would be affected whether he knew Batman personally or not.
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I don't consider a story a deathfic if the villain dies (i.e Luthor, SpencerX2, Metalo, etc.) and did die in canon, UNLESS that character is the main character of the story and the story is from his/her POV. Let's say, if Miranda from PML were to die within a PML remake that wouldn't make it a deathfic, unless Lois, Clark, Jimmy, or Perry were the cause of her death.
Sometimes I read deathfics and sometimes I do not. It usually depends on my mood and the type of death and/or if the author is one I know will treat the death and the aftermath for the survivors with respect and some realism. I usually don't like to see Lois or Clark waste away by illness. If the character dies at the end of a full and long life, then it isn't as bad, IMO.
In regards to your current story, Terry:
Lois's death was handled respectfully. While she was sick for many years, she still lived a full -- albeit, not a full-term -- life. She was able to get married, have children, and be a success in her career. The story is about her life, death, and how Clark survives losing her. In that regards it IS a deathfic, because of the main focus on her death.
I might also consider a story a deathfic if the story ends abruptly with someone's (see Mike's list) death. If someone dies within a story, I usually like the plot to continue on until the surviving characters have recovered (somewhat) and hope has restored. But that's me.
That being said, I might write or read a story which breaks all the above-mentioned rules, just to stretch myself as a writer or because the author is one I trust. (See Wrong Trilogy, Book 1: Another Dimension, Another Time, Another Lois... where... WHAM warning
Everyone dies... Or do they...?
Dark comedies can also be deathfics, but not everyone has the same sense of humor and might not find the humorous way you've found to kill off Lois or Clark as funny.
