Example: "Their love was so strong that it was unspoken. Words were (replace) 'not necessary' for them to display their affection towards one another.
They shared a tacit understanding. Words were gratuitous.
: expressed or understood without being directly stated
implied, implicit, unexpressed, unspoken, unvoiced, wordless
explicit, express, expressed, spoken, stated, voiced
: not necessary or appropriate
essential, indispensable, necessary, needed, needful, required
(Synonyms omitted -- none of the ones provided come close enough)
(From Merriam-Webster online)
you may say that their love was indescribable or beyond description
- Indescribable means impossible to describe, because too intense, extreme, etc, for words.
you may also speak of an overwhelming love.
- Overwhelming means very great in number, effect, or force, i.e. extreme. it is used to describe something that is so confusing, difficult, etc., that you feel unable to deal with it.