One definition says that any woman who sleeps with other women at least some of the time, without necessarily excluding other sexes is a dyke, as opposed to a woman who sleeps with other women exclusively, a lesbian.
The definition of either word is not supposed to be restricted by what type of woman you sleep with ie. womyn-born-womyn (bio-female) or MTF transsexual or bisexual ('traitor') or political dyke (ultra-feminist) or natural lesbian or LUG or straight woman or butch or femme, etc., but in 'the real world' such distinctions are often messily made.