Bullish and bearish are two commonly used terms in trading.
Investors are bullish on a particular asset if they have an optimistic outlook and expect or fell that asset price will increase.
Investors are bearish on a particular asset if they have a pessimistic outlook and expect or fell that asset price will decrease.
Traders can be bullish on an asset and bearish on another asset. They can also be bullish in a timeframe (daily for example) and bearish in another timeframe (monthly for example).
A bullish signal is an indication, usually generated by an indicator, that the asset price is expected to increase.
A bearish signal is an indication that the asset price is expected to decrease.