User Rubenerd shows us how to get Hunspell set up on your FreeBSD or macOS system. Hunspell, originally based on MySpell, is an open-source spell checker used for LibreOffice, Firefox, Thunderbird, as well as Adobe InDesign. See the link below for the full set of instructions.
Hunspell is an excellent spell checking library written by László Németh I only learned of since trying emacs. Yes, that’s happening! It’s also the spell checker used for LibreOffice, OpenOffice.org, and Mozilla applications. It requires installation of the library, and one or more word lists to compare words against.
On macOS you can use Homebrew or pkgin to get the latest version, but the dictionary files may be missing or outdated:
$ brew install hunspell # pkgin install hunspell
Installing Hunspell on FreeBSD and macOS: https://rubenerd.com/installing-hunspell-on-freebsd-and-macos/
Hunspell GitHub: https://hunspell.github.io/