SECBR (Severely Errored Cell Block Ratio) In asynchronous transfer mode (ATM), a dependabil- ity parameter expressed as the number of severely errored cell blocks (some number of cells transferred in a sequence) compared with the total number of cell blocks sent over a period of time. A severely errored cell block outcome is realized when more than some number of cells in a block is errored, lost, or misinserted. See also  ATM,  block, and  cell.  74570c19.qxd  9/12/07  12:41 AM  Page 431  |