The term 'understand, slangily' can be expressed in two different ways. The first is 'DIG, ' which is a three-letter word that has been used since the 1950s to mean 'to understand or appreciate something.' The second is 'GROK, ' which is a four-letter word coined by Robert Heinlein in his 1961 science fiction novel Stranger in a Strange Land. It means 'to understand intuitively or by empathy.' Both words are used to express the idea of understanding something without necessarily having to explain it.