Access concentration is another term that means different things to different people, and various criteria and definitions of it are used.

In general terms the way it tends to be used here is to mean something like the following:

• The level of concentration needed to be able to access the first samatha jhana, the first vipassana jhana and the insight stage Mind and Body.
• The level of concentration needed to actually stay with one's chosen object of meditation.

Various substantially more hardcore definitions may be found, particularly in circles that advocate very hardcore samatha practice, such as those put forward by practitioners such as Alan Wallace.