Based on existing reliable broadcast protocols in MANETs, we propose a novel reliable broadcast protocol that uses clustering technique and gossip methodology. We combine local retransmission and gossip mechanisms to provide reliability in MANETs. The proposed protocol can dynamically change system parameters for reliable broadcast communication in order to improve the adaptability in the rapidly changing network environment. In our proposed protocol, the adaptive gossip probability is explored to make the protocol insensitive to changing environment. In sparse or boundary areas, a large gossip probability is adopted in order to improve the reliability; while in dense or inner areas, a small gossip probability is used to alleviate the contention and collision. Theoretical analysis shows that the proposed protocol has high delivery ratio and low end-to-end delay for broadcasting.