1Colloquially, to get on or climb onto something (or someone's back); figuratively, to piggyback on someone else's idea or trend.
子どもがソファの上に乗っかって飛び跳ねている。
The child is jumping on the sofa.
荷物が多くてトラックの荷台に乗っかるしかなかった。
There was so much luggage we had no choice but to ride on the truck bed.
彼の成功に乗っかって同じビジネスを始めた人がいる。
Some people started the same business piggybacking on his success.
危ないから誰かの肩に乗っかるのはやめなさい。
Stop standing on someone's shoulders — it's dangerous.