The endless cycle of birth, existence and death.
However, that is a lot of concept to pack into one word. How did they arrive at the word "samsara" to encapsulate such a complex concept?
"endless cycle of death and rebirth, transmigration of souls," 1886, from Sanskrit samsara "a wandering through," from sam-, prefix denoting completeness (from PIE root *sem- (1) "one; as one, together with"), + sr- "to run, glide" (from PIE verbal stem *ser- "to flow;" see serum).
But I don't know how I feel about PIE yet, not sure how they arrive at these derivations. Tangential question: it says 1886 is the latest definition, when does the word first get used?
If I were to go with etymonline's derivation, of sem and serum, it is the "one flow" basically, being one with the flow, being tied to the flow. But I don't know if that is a correct interpretation.
But the main question is, what do the components of the word mean. Is there any Buddhist text that elaborates on this concept and ties it back to the word more deeply? If so, what text is it and/or what do they generally say?