What does Picasso's painting, "The Old Guitarist" mean or represent?
Grief and depression.
Picasso painted The Old Guitarist in 1903, during his Blue Period (1901-03). He had left Barcelona with his friend Carlos Casamegas in favor of the risk and uncertainty of a painter's life in Paris. No one was interested in his paintings, and many of his early works were rolled up and burned to keep him from freezing to death. Understandably, he was sad.
Casamegas fell in love with Germaine Pinchot (Casamegas and Pinchot were both models for some of Picasso's early paintings), but she did not return his feelings and he shot himself. Picasso's grief for this affected his art for two years, and The Old Guitarist was painted towards the end of this period.
Picasso's professional career is generally divided into seven distinct periods: Blue, Rose, Black (African-influenced), Early Cubism, Synthetic Cubism (All these were before 1920), Classicism and Surrealism (roughly 1920-1945), and Later Works. The Old Guitarist is the most emblematic of his earliest period.