I uninstalled the default/stock Terminal app via AppCleaner. How to get the default/stock Terminal back without reinstalling Mojave?
You can restore it from your backup. Because you wouldn't start deleting bits of the system with a third-party app without making sure you had a backup.
Failing that, you can reinstall the OS over the top of your existing installation, and all your files, apps and settings will still be in place. This will make sure that anything else important that ApplCleaner has deleted will be restored.
Some people do this from time to time, just to make sure nothing's got corrupted or missing.
I don't think there is a way to access the terminal app without reloading the operating system. If you have terminal on another machine you may be able to copy the app to your computer.
An easier solution would be to use iTerm2. Its a terminal emulator like terminal but with more features. Its considered by many as a better emulator than Terminal. I use it myself in place of the Terminal app.