Just as native speakers face new words or concepts in their own language when they attend a lecture, watch a movie or speak with a friend or colleague, you as a Second Language learner will need to overcome your limitations in speaking, understanding or writing, by using certain Compensation Clues. A native speaker usually meets fewer of these in his or her day, but the method is the same when faced with the knowledge that you don't know something or can't understand a word or phrase.
We overcome these limitations by getting help. Yes, it is a real-world practice, and it is permitted. We find a friend, an interpreter or a bilingual dictionary, for example. Get help.
Then we might use a circumlocution, synonym or a talk-around. Kind of like explaining, but different.
Or we can switch to mother tongue, if this will facilitate understanding. Might not, but it's worth a try.
Sometimes we can get over the glitch with mime or gesture, hands or face. It works, when your partner WANTS to know what you're trying to say.
Another workaround is for us to choose the immediate topic, that WE can talk about, which may or may NOT closely correlate to what needs to be discussed.
We can approximate or adjust our message, lightening up on details and only transmitting core meaning: instead of "Please cease and desist in your actions with that" we adjust to "Don't do that!" or even (in some languages) "Don't!"
And finally we can coin new words in the target Second Language. Hey, I've done it before, with mixed results. It might work, and I know it has worked on occasion, but just as often this leads to a break in the communicative logjam by evoking the wrong response in the listener. But don't sigh, because when you once learn that your partner has not understood what you wanted to impart, you then have a contextual benchmark from which you can anchor and work.