What did David Axelrod mean by "word salad"?

Obama's long-time chief campaign strategist, Axelrod yesterday derided Harris for having difficulty answering basic questions on the campaign trail (even when asked by friendly faces)...and resorting to "word salad" response.

What was he talking about? Today, Anderson Cooper asked a very simple question. "You didn't like Trump's idea to build a border wall but now want to spend $600 million building one. How is that?".

Her answer illustrates the problem of which Alexrod speaks. No bueno!