Definition - What does Irrelevant mean?
Irrelevant means that something is not important or related to the issue that is being discussed.
If an attorney thinks that the information being given in a particular testimony is irrelevant, then they may try to get the judge to dismiss it. Sometimes the judge agrees, and sometimes the judge does not agree. The dismissal depends on the judge's opinion.
Justipedia explains Irrelevant
An example of an irrelevant part of a testimony may be a witness of a bank robbery bringing up the fact that they saw an auto accident outside the bank 20 minutes before the robbery. In this case, the accident would likely be completely irrelevant to the bank robbery. The defense attorney may therefore object due to irrelevance. If the judge agrees that it is irrelevant, they may ask the witness to stay more on the topic of the robbery.