segment_define is in the heirarchy of segment creation, for which you will also need:
segment_vectors_*segment_define(segment_filters, not_vector = NULL)dynamicSegment,
orFiltersForSegment,
segmentDefinition,
segmentDimensionFilter,
segmentFilterClause,
segmentFilter,
segmentMetricFilter,
segmentObj_ga4,
segmentSequenceStep,
segment_element,
segment_vector_sequence,
segment_vector_simple,
sequenceSegment,
simpleSegment