module.exports = {
  // some nuxt config...
  plugins: [
    { src: '~/plugins/swiper.js', ssr: false },
  ],
  // some nuxt config...
  css: [
    'swiper/dist/css/swiper.css'
  ],
  // some nuxt config...
}

module.exports = {
  // some nuxt config...
  plugins: [
    { src: '~/plugins/nuxt-swiper-plugin.js', ssr: false },
  ],
  // some nuxt config...
  css: [
    'swiper/dist/css/swiper.css'
  ],
  // some nuxt config...
}

Fix pluginfile name