Ryū (竜,Ryū?) is Japanese for "dragon" and can be found in the Japanese term for "dinosaur", kyōryū (恐竜,kyōryū?), and dinosaur-related terms, such as yokuryū (翼竜,yokuryū? "pterosaur").
Strengths and Weaknesses
A user of this fruit's power can turn into a pteranodon: a large and powerful, flight-capable reptile from prehistory. Once transformed, they become able to fly at tremendous speed, covering large distances in a short time, and gain a significant boost to their overall physical abilities, as expectable of a predatory Ancient Zoan. Additionally, the full Beast Form as displayed by King is notably big, several times larger than an average-sized human (though it is worth noting that King is already much larger than normal people in his human form).
The combination of great (flight) speed, strength, and size conferred by the transformation permits the user to violently push back and cause notable damage to whatever they fly into headfirst, be it a person or massive structure, such as a large ship. The user's pteranodon beak is long, sturdy, and an effective pointed weapon, allowing King to affix himself to smaller targets and then divebomb into structures in order to tear them apart.
No weaknesses are known of this ability beside those that are standard for Devil Fruits.
King uses his ability for battle, namely aerial combat (apart from the power's general suitability for flight-based travel). In his full Beast Form, he is able to fly into objects with immense speed and force, potentially damaging them greatly in the process. When flying into the Queen Mama Chanter, such midair collision (with a flaming kick in the anime) knocked the enormous ship back with enough force to throw off Big Mom herself.
Later, King was shown to present a danger to a Raid Suit-wearing Sanji by diving into him with his strong, sharp-pointed beak, challenging said suit's defenses to the point that King claimed he would split his foe in half upon impact (something he ultimately failed at due to the suit proving too durable).
King possessing this fruit's ability and his "Conflagration" epithet evokes a resemblance to the kaiju Fire Rodan, a pteranodon residing in a volcano, which is among the major reoccurring kaiju in the Godzilla franchise.