Maya Angelou recounts details of her surprise meeting with Martin Luther King Junior in her "Encounter with Martin Luther King Junior." In The Heart of A Woman, Angelou discusses this meeting and others she had with other prominent activists such as Malcolm X.
Her description of Martin Luther King Junior paints a picture of a strong man, passionate about his cause and also a humble man with a sympathetic ear.
To describe Martin Luther King Jr from this encounter and in three words, you could concentrate on the physical characteristics Angelou mentions such as "short....young...." and "good looking" which are supported in the text when Angelou recalls, He was shorter than I expected and so young." Later she will refer to him most certainly as having been a "school athlete."
Other than his physical attributes, Angelou ensures that the reader can appreciate King's character. She explains how he shows empathy - so he is empathetic - when he hears of her brother's incarceration in "Sing Sing," a prison. He is interested in Angelou's descriptions of her earlier life when she talks about her grandmother (Mamma) and her uncle "as if he knew them personally." This makes him sincere and interested.
The last series of three words that could be used to describe King from Angelou's meeting refer to his strength and commitment to the cause but ever humble. He is like a "lion sitting down...eating greens" confirms his strength and his humility.(Lions would not be eating "greens" ordinarily.) He talks about "the firing-line" which reinforces his commitment despite the difficulties.