If you call going from $1000 to $19,000 in a year then declining sharply a bubble, then sure, it's a bubble.
Bitcoin is not a bubble, it's just that he has too high a volatility. 
Five facts, according to Nasdaq, why bitcoin is not a bubble:
1. The Growing Acceptance of Bitcoin as Legal Tender
2. Increasing Merchant Adoption
3. Bitcoin Is Increasingly Acting as a Store of Wealth in Distressed Economies
4. Bitcoin Has Only Just Gone Mainstream
5. Bitcoins Supply Is Limited