"Sending data" taking too much time (no replies)

We have been in the process of trying to profile a couple of SQL queries that were taking 6-7 sec. The result from the MySQL profiler looks like this:

+--------------------+-----------+----------+------------+

| Status | Duration | CPU_user | CPU_system |

+--------------------+-----------+----------+------------+

| (initialization) | 0.0000012 | NULL | NULL |

| Opening tables | 0.0000277 | NULL | NULL |

| System lock | 0.000004 | NULL | NULL |

| Table lock | 0.0000062 | NULL | NULL |

| init | 0.0000212 | NULL | NULL |

| optimizing | 0.0000074 | NULL | NULL |

| statistics | 0.000012 | NULL | NULL |

| preparing | 0.000011 | NULL | NULL |

| executing | 0.0000027 | NULL | NULL |

| Sending data | 6.9561519 | NULL | NULL |

| end | 0.0000062 | NULL | NULL |

| query end | 0.0000037 | NULL | NULL |

| freeing items | 0.000007 | NULL | NULL |

| closing tables | 0.001863 | NULL | NULL |

| logging slow query | 0.0000875 | NULL | NULL |

+--------------------+-----------+----------+------------+

15 rows in set (0.00 sec)

What does "sending data" here mean? And what should be tuned to reduce this?