It means it hasnt been flushed properly (chemicals still in the bud). If you really want to stop it, you can watercure it. This just means putting the bud in water, making sure its completely submerged. Each day change the water, and do this for 5 to 7 days. Let it dry in a cool, dark place with plenty of ventilation for between 2 to 7 days (just until its dry) and then smoke. You wont lose any potency as THC isnt water soluble, and you wont get any headaches that occasionally come from smoking the chemicals. Alternatively, you could use a vaporiser - but for the love of God, Shiva and Buddha, dont use a lightbulb vape. Theyre cheap, theyre tacky, and theyre shite.