Teaching sketch. It shows the shape, not a live quote and not a trade signal.
Definition
A lower low is a decline that extends beyond the previous decline. The market accepted a cheaper price. Repeated lower lows, with lower highs, are a downtrend. A lower low after a series of higher lows is a possible break of an uptrend.
How to identify it
Use the same swing rule as for the highs. A wick under the old low that closes back above it is a sweep or a false break unless your rule counts wicks. Write the rule down.
Bullish reading
A lower low that immediately reclaims the old low can be a stop run, the raw material of a reversal. The bullish case is the reclaim, not the lower print itself.
Bearish reading
Lower lows confirm that supply is still finding new prices. In a downtrend they are normal, not an automatic place to buy.
Common mistakes
Buying every lower low as "support broken, so it must bounce." A lower low is often the trend doing what trends do.
Limitations
The final lower low of a trend looks like all the others while it is printing. You identify it later, by the higher high that follows.
This note explains the term. A sketch shows the shape of the idea. Neither is a recommendation, a signal, or a comment on any security. Indicator settings and exchange conventions differ. Check the live chart and the contract specification before you use a number.