I read jisho a lot and I run into words with outdated kanji. Does this mean that the kanji term is outdated for a particular word or all words that use it?
(oK) stands for "word containing out-dated kanji". This simply means that nowadays the word is not written with these kanji. It does not say that these kanji are "out-dated" (whatever this would mean), just that they are out-dated for writing the particular word listed.
As an example, look at the entry for 遡る
さかのぼる 《遡る(P); 溯る; 逆上る(oK); 泝る》 (v5r,vi) (1) (uk) to go upstream; (2) (uk) to go back (in time, to origin); to date back to; to trace back to; to make retroactive; (P)
(P) indicates that 遡る is a ""Priority" entry, i.e. among approx. 20,000 words deemed to be common in Japanese". It can also be written 溯る, 逆上る, or 泝る. (The colour coding (see above link) says that 溯 and 泝 are not jōyō kanji.)
However, even though 逆 and 上 are jōyō kanji with jōyō readings 逆【さか】 and 上る【のぼる】, the kanji representation 逆上る【さかのぼる】 is out-dated, which is indicated by the code
(Of course the etymology of sakanoboru is just saka + noboru and might well have been written 逆上る, but nowadays it just isn't. See Kanji for native Japanese concepts: Kun'yomi spanning multiple morphemes for similar such words.)