Synonyms are provided when using Microsoft Editor spell checker

The Microsoft Editor service provides enhanced spell and grammar checking for editable text fields on web pages, and synonyms can be suggested as an integrated feature.

If you enable this policy, Microsoft Editor spell checker provides synonyms for suggestions for misspelled words.

If you disable or don't configure this policy, Microsoft Editor spell checker won't provide synonyms for suggestions for misspelled words.

If the 'SpellcheckEnabled' (Enable spellcheck) policy or the 'MicrosoftEditorProofingEnabled' (Spell checking provided by Microsoft Editor) policy are set to disabled, or the user disables spell checking or chooses not to use Microsoft Editor spell checker in the settings page, this policy will have no effect.