expatiate vs talk at

expatiate

verb
  • To write or speak at length; to be copious in argument or discussion. 

  • To range at large, or without restraint. 

talk at

verb
  • To speak with; to have a conversation with. 

  • To speak with (someone) without truly listening to their response or interacting meaningfully. 

How often have the words expatiate and talk at occurred in a corpus of books? (source: Google Ngram Viewer )