Bubble in currency/capital market means sudden rise or sudden fall in price. How bitcoin is a bubble? Bitcoin`s price is rising continuously since last two or more years. It has increased its pace in the month of December last year but that was not new to bitcoin currency. Increase ans correction in price are the basic needs of any currency. After reaching $19000 price tag, profit booking started, which was expected by its investors. Many bitcoin opponents predicted bitcoin will crash and will vanish from market. Nothing like that happened, bitcoin price slipped upto $10000 mark and settled there. Now  once the correction mood is over it will start raising again.