The term 'understand, in slang' can be expressed in two ways. The first is 'GROK, ' which is a four-letter word derived from Robert Heinlein's 1961 science fiction novel Stranger in a Strange Land. It means to understand something intuitively and deeply. The second is 'getthedrift, ' which is an eleven-letter phrase meaning to understand something without needing to be explicitly told. Both of these slang terms are used to express the idea of understanding something without having to be told directly.