forgettable
So ordinary or dull that people quickly forget it.
Something forgettable is so ordinary or unimpressive that it doesn't stick in your memory. A forgettable movie might be okay while you're watching it, but a week later you can barely remember what happened. A forgettable meal fills your stomach without being good enough or bad enough to remember.
The word usually carries a mildly negative feeling. When a book reviewer calls a novel forgettable, they mean it wasn't terrible, but it wasn't interesting or well-crafted enough to leave a lasting impression. After reading dozens of books, the forgettable ones blur together while the memorable ones stay vivid in your mind.
Everyone has forgettable moments too: days that were fine but nothing special, conversations that were pleasant but unremarkable. There's nothing wrong with forgettable experiences. They're just the ordinary background of life. But when you work hard on something, like a presentation or a story, you naturally hope it won't be forgettable. You want it to matter enough that people remember it.
The opposite of forgettable is memorable or unforgettable. When something is truly unforgettable, it's so powerful, surprising, or meaningful that it stays with you for a long time.