An “adventure” is an exciting or unusual experience usually involving some risk.
Some people fear going on long trips along unknown roads to unknown places. Their fear increases if you suggest travelling solo. I respect their apprehension and do not try to convince them otherwise. The world runs on people who prefer living in their perceived safe space and travelling in groups to visit well worn tourist destinations.
I enjoy travelling solo and I also enjoy travelling with someone or a group of 4 or less vehicles who share the same attitude towards adventure trips. While I do travel with larger groups and enjoy the social side of this, I do not enjoy the long waits during vehicle fuelling, shopping, border crossings and unprepared travellers who take advantage of their fellow traveller’s generosity – The larger the group, the longer the wait and the greater the chance of having to travel with someone you would rather avoid.
I wish I could find the right words to explain why I love to go on long solo adventures. Until I find my own words, Eglė / @EvergreenE's article "On The Road / Things No One Tells You About Long-Distance Riding" in Adventure Rider probably explains this best.