What is "to reckon without one's host"

Reckon \Reck"on\, v. i.

1. To make an enumeration or computation; to engage in numbering or computing.
   --Shak.

2. To come to an accounting; to make up accounts; to settle; to examine and strike the balance of debt and credit; to adjust relations of desert or penalty. ``Parfay,'' sayst thou, ``sometime he reckon shall.'' --Chaucer. To reckon for, to answer for; to pay the account for. ``If they fail in their bounden duty, they shall reckon for it one day.'' --Bp. Sanderson. To reckon on To reckon upon, to count or depend on; to include as a factor within one's considerations. To reckon with,

   1. to settle accounts or claims with; -- used literally or figuratively.

   2. to include as a factor in one's plans or calculations; to anticipate.

   3. to deal with; to handle; as, I have to reckon with raising three children as well as doing my job.

      After a long time the lord of those servants cometh, and reckoneth with them.
      --Matt. xxv. 19.

      To reckon without one's host, to ignore in a calculation or arrangement the person whose assent is essential; hence, to reckon erroneously.