also: ポンプ
The kanji spelling 喞筒 is an archaic ateji form; the modern word is ポンプ. The reading そくとう (and variant しょくとう) are historical Sino-Japanese readings of these characters, not used in contemporary language.
See also: ポンプ
The characters 喞筒 can be found in old documents as ateji for 'pump'.
Standard modern Japanese word for 'pump', a loanword from Dutch 'pomp' or English 'pump'. This is the practical spelling learners should use.
The kanji 喞筒 are ateji (characters used for their phonetic value) representing the word 'pump'. The readings そくとう and しょくとう are Sino-Japanese readings of these characters, but the word itself is a loan from a European language (likely Dutch 'pomp' or English 'pump'), now standardly written in katakana as ポンプ.