I have stage 4 Prostate cancer but I'm currently in remission (since Aug 25). My prognosis is 4-5 years

Nationwide/Aviva travel insurance says the following under the "What is not covered" part of the policy document - "

"Any insured person booking a trip or travelling when they have received a terminal

prognosis"

They do not define what a terminal prognosis is despite the fact that their document is 50 pages long!

I had a look on Google AI and this is what I found 

"Aviva Nationwide FlexPlus travel insurance generally excludes coverage for trips booked or undertaken after receiving a terminal prognosis. A terminal prognosis is typically defined in this context as an incurable condition with a life expectancy of less than 12 months, or as advised by a medical professional"

I think it's irresponsible for them not to include a definition.

Has anyone investigated this?