Definition of can't begin to tell you
- I can't begin to tell you how grateful I am for all your help.
: can not
: to do the first part of an action : go into the first part of a process : start
: to come into existence : arise
: to have a starting point
: to relate in detail : narrate
: to give utterance to : say
: to make known : divulge, reveal
: an inadvertent behavior or mannerism that betrays a poker player's true thoughts, intentions, or emotions
: hill, mound
What made you want to look up can't begin to tell you? Please tell us where you read or heard it (including the quote, if possible).