There are indicators which can help define whether a market is overbought. I use RSI in daily trading and it proves reliable if read correctly. Many people don't agree that technical analysis is relevant to Bitcoin, I disagree.
This simple chart shows the RSI and Fibionacci retracement indicators for Bitcoin for the last three months.
The retracement lines help to show where bounces within the down trend might reach before failing. As you can see, Bitcoin could rise to around 310 and still have only retraced 50% of the recent move down from the 420+ highs of November.
The dips below the RSI red line show when it became oversold and rallied.
In conventional RSI reading, the downtrend will stay intact until a reading of over 50 is established, currently about 42, a level which has more or less been a lid on it for the last month.

TL:DR
So, no, I don't think it's overbought yet, but it's still in a down trend.