predictive text options
can apple use all the words in the oxford english dictionary for predictive text as a default so user will utilise unfamiliar words
Predictive text is an AI-based prediction based on your usage of words in the past. The text which Siri learns from the usage of the device. It starts off with a certain set of words and keeps building based on your usage.
What you are looking for can be accomplished by Look Up, if you have enabled it.
See the pic below which is self-explanatory