1.
Also,
hold on to. Maintain one's grip, cling, as in Hold on to your hat in this wind, or The early Christians held on to their beliefs despite strong opposition. [Early 1500s]
2.
Continue to do something, persist, as in Please hold on for a while longer. [Late 1800s]
3.
Stop, wait, as in Hold on! We can't go past this gate. [Mid-1800s]
4.
Remain on a telephone line, as in If you can hold on a minute I'll go and find her. [Late 1800s]