Inspired by Krashen's i+1 hypothesis and yomitan (a Japanese popup dictionary) my friend an I made a chrome extension that provides you with a custom definition of any word or phrase you encounter on the internet.

Custom because in addition to adapting to the context of the text, you can also adapt the difficulty level of your definition. This is great if you are an intermediate language student and want to go monolingual, but are struggling with the full native level dictionary definitions.

(P.S. there is also a science version that explains the highlighted text at multiple levels... think Wired's 5 levels More info about the tool at https://incontext.fun)