"to risk" and "to venture" are both in the dictionary
see: https://jisho.org/word/%E5%86%92%E3%81%99
also since this is mainly intended as a dictionary for English speakers it's not always necessary to list all possible English meanings
if you still want to add definitions which you think are necessary you can click on the "Links" button of an entry to edit it and add more meanings
I think that's not a very productive approach to learning a foreign language. Rather than expecting to find a one-for-one translation of every old-fashioned usage (like "hazard" as a verb) that only survives in a specific expression in English that may or may not even translate literally into Japanese, better to just try to find the Japanese equivalent expression that may or may not include the equivalent of that word.
Words or definitions that are missing from Jisho
This site is a very useful resource. Occasionally, I come across a word or meaning that is missing in one language or the other. I will use this forum to list those to see if someone can suggest remedies;
to begin;
"Hazard" is also a verb as in "hazard a guess"
"venture" and "risk" are also verbs with the same sense