I googled , here is the definition: Invalid noun a person made weak or disabled by illness or injury. "an invalid husband" synonyms: ill, sick, ailing, unwell, infirm, valetudinarian, valetudinary, in poor health, incapacitated, disabled, handicapped, bedridden, frail, feeble, weak, debilitated, sickly, poorly, ill person, infirm person, sick person, sufferer, patient, convalescent I think back in the "old days" it was synonymous with the modern word "disabled" of our day and was just descriptive. But nowadays it seems like some use the word invalid as a curse word towards someone disabled. It depends on how someone used the word and in what spirit they say it toward someone disabled. In general, I don't like the word invalid, probably because of Hollywood using those words in movies by some characters in a derogatory fashion towards someone else or even themselves if the character was dealing with an illness or maimed in some way. That's what comes to mind for me. More on reddit.com

I think it depends on the context. It is accurate when describing a person who has a long term chronic illness that basically leaves them bedbound. For example: Ignoring their exercise intolerance can cause a person with ME/CFS to end up as an invalid. However, because it isn't in common usage outs easy to misinterpret as in-valid. Which is a crappy thing to say about someone. So, to be safe, you can use the term bedbound instead. More on reddit.com