In this case, the substance is the atmosphere. When the atmosphere absorbs energy, the result is an irreversible transformation of radiation into another form of energy. This energy is transformed according to the nature of the medium doing the absorbing. The absorbing medium can also do much more. The medium will only absorb a portion of the total energy.
Drawn from a book title, the phrase has taken on a broader meaning. If you've paid any attention to business in the last few years, it's likely that you've heard a lot about leaning in. Headlines and book titles encourage us to lean in to innovation, or tell companies to lean in, or detail education without leaning in..
(uncountable and countable, rhetoric) The use of a word or phrase to refer to something that it is not, invoking a direct similarity between the word or phrase used and the thing described (but in the case of English without the words like or as, which would imply a simile); the word or phrase used in this way; an implied comparison.